Development of trigonometry learning kit with a STEM approach to improve problem-solving skills and learning achievement

This study aimed to produce the trigonometry learning kit for tenth-grade high school students using the STEM (Science, Technology, Engineering, and Mathematics) approach properly. This study was development research using the ADDIE model, which consisted of five stages, namely Analysis, Design, Development, Implementation, and Evaluation. This study’s subjects were tenth-grade high school students ( n = 32) in Semarang, Indonesia. Data collec-tion was carried out through questionnaires and tests. To assess the learning kit’s validity, we used a questionnaire with the expert (mathematics education lecturers) as data sources. To assess the learning kit's practicality, we used the questionnaire (with teacher and student as data sources) and observation sheets. We used a test to assess the learning kit's effectiveness in terms of problem-solving skills and learning achievement. This development resulted in the trigonometry learning kit in the form of lesson plans or Rencana Pelaksanaan Pembelajaran (RPP) and worksheets or Lembar Kegiatan Peserta Didik (LKPD) using the STEM approach properly (meet the criteria of being valid, practical, and effective). The learning kit characteristics were: facilitating problem-sol-ving skills and learning achievement, using problems related to Science, Technology, Engineering, and Mathematics, and organizing based on Engineering Design Process (EDP) steps. calculation on the problem-solving skill test results shows that the increase in students’ problem-solving skills after learning using the STEM approach is in the high category. Therefore, the learning kit developed to fulfill the effectiveness criteria is based on students’ problem-solving skills and learning achievement.


INTRODUCTION
The 21st-century competition requires Human Resources to be competent in science, technology, engineering design, and mathematics (Milaturrahmah et al., 2017). Trilling and Fadel (2009) state that 21st-century skills demand competent human resources in learning and innovation skills; information, media, and technology skills; and life and career skills. High school graduates should be proficient in the dimensions of science and technology (Ministry of Education and Culture, 2016a, p. 4). Hence, every individual must master not only one discipline. Learning uses the STEM approach in line with the expectations of the Curriculum 2013 regarding proficiency standards for secondary school graduates and 21st-century requirements. STEM combines some or all of the four disciplines from science, technology, engineering, and mathematics with real-world problems (Dare et al., 2018, p. 1). Torlakson (2014, p. 7) states that implementing STEM's objectives includes the need for the nation to increase the number of STEM experts to encourage innovation and keep a country competitive in the global Non-routine problem-solving strategies that arise during the learning process encourage students to think deeply about mathematical concepts related to the given problem (Wisniarti & Sugiman, 2018, p. 1). The problem-solving skill of Indonesian students is low, it is seen from the 2012 PISA results (OECD, 2014, p. 19), the difference in score per unit index of openness to problem-solving, Indonesia scored 7, while the OECD average of other countries was 31. Students' mathematical problem-solving can be trained and developed when the teacher can choose approaches, models, methods, or appropriate learning strategies and follow the material, situations, and conditions of students in learning (Siregar et al., 2018, pp. 464-465).
A learning kit is a form of preparation made by the teacher before carrying out the learning process (Tamba et al., 2019, p. 2). The key tasks involved in classroom teaching can usefully be grouped under three main headings: 'planning', 'presentation and monitoring', and 'reflection and evaluation' (Kyriacou, 2009, p. 86). Moon et al. (2002, p. 54) state that effective teachers are very systematic in preparing and implementing each lesson. The learning kit developed in this study focus on a lesson plan or RPP and worksheet or LKPD. RPP is a description of how the teacher directs student learning activities to achieve certain goals and functions as a framework to guide students to these goals (Vdovina & Gaibisso, 2013, p. 58). Ormrod et al. (2017, pp. 442-443) state that the preparation of RPP needs to consider several things from the students who will learn, namely the level of development, previous knowledge, cultural background, and other special educational needs. There are seven domains of lesson planning, namely: alignment with standards, appropriate learning objectives, opening and warming up, learning activities, closings, methods for measuring student understanding, instructional support for various students (Lim et al., 2018, p. 527). Besides RPP, students also need LKPD in the learning process. LKPD, according to Choo et al. (2011, p. 520), is a teaching kit that consists of a set of questions and information to guide the students to understand the material when they work systematically. LKPD are written materials containing explanations that guide activities that students will take in teaching any topic (İnan & Erkuş, 2017(İnan & Erkuş, , p. 1373. Worksheets can be useful in many ways in terms of academic achievement, as a supplement to textbooks, to add information (Lee, 2014, p. 96).
Some teachers have used learning approaches or models that are tailored to the material being studied by students. However, RPP and LKPD have not been prepared to improve certain skills and have not used the STEM approach. STEM is suitable for Indonesia because STEM conforms to the Curriculum 2013 as an applicable curriculum in Indonesia (Arlinwibowo et al., 2020, p. 608). The STEM approach is an approach that combines two or more fields of science contained in STEM, namely, Science, Technology, Engineering, dan Mathematics (Khoiriyah et al., 2018, p. 54). Learning that integrates the STEM approach allows students to experience their learning process. The knowledge they can absorb and store into memory longer, the students' knowledge and understanding are more significant because the results themselves and not only receive information (Suherman et al., 2018, p. 2). Several STEM studies usually integrate the STEM approach with other learning approaches or models such as STEM through Engineering Design Process (EDP) (Winarno et al., 2020(Winarno et al., , p. 1346). An engineering design process integrates science, mathematics, and technology (Jolly, 2017, p. 25). According to Jolly, the EDP steps consist of defining the problem, research, imagine, plan, create, test and evaluate, redesign, and communicate.
Accessing STEM inspires students to think about its application in the real world (Roberts et al., 2018, p. 8). The integrated STEM approach can motivate students to pursue careers in STEM and increase their interest and performance in mathematics and science (Stohlmann et al., 2012, p. 32). The STEM-based PBL learning model's application can improve the problem-solving skills of XI Science of MA Nasruddin Dampit (Amelia et al., 2019, p.15). Research conducted by Suherman et al. (2018, p. 7) shows that students who get a STEM approach in learning have a better understanding of trigonometry concepts than students who get conventional learning. It shows that students who get a STEM approach better understand the trigonometry concept than those who receive conventional learning. Furthermore, the integration approach among STEM has a positive effect on student achievement (Becker & Park, 2011, p. 25). The STEM approach can further improve problem-solving skills with an increase in Ngain of 0.67 in the moderate category (Lestari, 2019, p. 108).
Research related to the use of the STEM approach in learning is mostly found in science disciplines (Acar et al., 2018, Khoiriyah et al., 2018, Lestari, 2019, Lestari et al., 2018, Sarnita et al., 2019, Syukri et al., 2013, Yaki et al., 2019. The following is research on STEM in mathematics. Previous research describes the integration of the STEM approach in quadrilateral material (Utami et al., 2018), linear program material (Amelia et al., 2019), and three-dimensional material (Bakhtiar et al., 2020). Research Suherman et al. (2018) found out the increased comprehension of trigonometry concepts between the students who received STEM learning, and the who received conventional learning. Their research does not indicate that the learning kit's quality is used and not oriented to specific skills.
Based on the background, learning with the STEM approach has many theoretical benefits, especially learning achievement and problem-solving skills. Wang et al. (2011, p. 2) stated that one challenge of learning with the STEM approach is the lack of general instructions or examples for teachers to teach using the classroom's STEM approach. Therefore, the development of a learning kit is needed. The development of a learning kit with the STEM approach is a form of support for the demands of the 21st century that require competent human resources and following the expectations of the Curriculum 2013 regarding the competency standards of high school graduates. Therefore, trigonometry learning kit using the STEM approach is expected to be attractive alternative learning kits and can improve problemsolving skills and learning achievement. Therefore, this study aimed to produce a trigonometry learning kit for grade X SMA students using the STEM approach and describe the quality of the developed learning kit in terms of validity, practicality, and effectiveness.

This research was research and development (R & D)
. The R & D method was a research method used to produce certain products or test their effectiveness (Sugiyono, 2015, p. 407). Meanwhile, Gay et al. (2011, pp.17-18) defined research and development as the process of researching and developing products to meet needs. There were many learning development models, but the developing learning kit in this study was referred to as the ADDIE model (Molenda & Boling, 2008, p. 110). This model consists of five phases: Analysis, Design, Development, Implementation, and Evaluation. The study's subjects were 32 students of tenth-grade in senior high school (SMA Negeri 5 Semarang), Indonesia. They consisted of 13 boys and 19 girls with heterogeneous characteristics. The research was conducted for seven meetings from April 2020 to May 2020. The first meeting was held pretest, the next five meetings were conducted with learning, and the last meeting was held posttest. In connection with the implementation of research during the COVID-19 pandemic, research activities were conducted online. The test was given using a Google Form while learning uses WhatsApp and Google Meet media.
Data were collected through questionnaires and tests. The questionnaire was a non-test instrument in the form of a set of questions, usually in written form and then given to respondents (Retnawati, 2016, p. 3). The questionnaire I was used to assessing the learning kit's validity level with expert lecturers as data sources. Questionnaire II was used to assess the practicality of the learning kit from teachers and students. The test was used to measure the effectiveness of the learning kit. We convert quantitative data into qualitative data based on Table 2 and Table 3 (Retnawati et al., 2017, pp. 127-128).
The learning kit's quality was determined based on validity, practicality, and effectiveness criteria (Nieveen, 1999, p. 127). According to Plomp and Nieveen (2010, p. 28), product quality was said to be valid if it meets needs, the components were based on up-to-date knowledge (content validity), and all components were consistent with each other (construct validity). According to Plomp and Nieveen (2010, p. 28), product quality was practical if it made it easy for teachers and students to use the product and follow the developer's intent. According to Plomp and Nieveen (2010, p. 28), the product's quality was said to be effective if the results were achieved as desired. Normalized gain (N-gain) as a measure of the effectiveness of a lesson (Hake, 1999) and was used to assess student performance on the initial and final tests (Bao, 2006, p .917).
The learning kit's validity was assessed using a questionnaire to choose a rating scale of 1 (not good) to 5 (very good). The assessment of the RPP instrument's validity consists of 32 items, and the assessment of the validity of the RPP instrument consists of 26 items. The assessment aspects of RPP validity were RPP identity, competence attainment indicators, learning objectives, the suitability of material, learning activities, the suitability of media, or learning resources, assessment of learning outcomes, and language use. The assessment aspects of LKPD validity were identity and guidance, indicators and learning objectives, the suitability with learning achievement, the suitability with the problem-solving skill, the suitability of content and material, layout, language conformity, the suitability of presentation component, and benefits of LKPD. The learning kit's practicality was obtained from student assessment sheets, teacher assessment sheets, and learning implementation sheets. The teacher assessed the RPP and LKPD practicality by giving a checkmark on each statement's item to choose a rating scale of 1 (very bad) to 5 (very good). The practicality assessment of the RPP consists of ten items, and the practicality assessment of the LKPD consists of nine items. Students assessed the LKPD practicality by giving a checkmark on each statement's item to choose a rating scale from 1 (strongly disagree) to 5 (strongly agree). The LKPD practicality assessment consists of ten items. Meanwhile, learning implementation observation results were measured for each meeting, teacher activity, and student activity.
The effectiveness of the learning kit was measured using the problem-solving skills and learning achievement test. N-gain was used to measure a lesson's effectiveness (Hake, 1999) and assess students' performance on the initial and final tests (Bao, 2006, p.917). The level of N-gain (Hake, 1999) can be classified as follows, if g ≥ 0.7, then the resulting gain was in the high category; if 0.3 ≤ g < 0.7, then the resulting gain was in the medium category; and if g < 0.3, then the resulting gain was in the low category. The problem-solving skill test consists of five essay questions, and the learning achievement test consists of ten multiple-choice questions. Figure 1 and 2 was one item on each test. The question was then measured for validity and reliability. Based on content validation by two Mathematics Education lecturers from Yogyakarta State University, both tests were valid. The problem-solving skill test has a reliability of 0.816 with a very high category, and the learning achievement test has a reliability of 0.622 with a high category.
The learning kit was valid if each component meets the minimum good category, practical if it meets the minimum good category, and the percentage of learning implementation at each meeting was at least 80%, and effective if the N-gain was obtained at least moderate category.

Description of Learning Kit
The learning kit developed is RPP and LKPD on trigonometry material. RPP components are developed according to the Regulation of the Minister of Education and Culture Number 22/2016 (Ministry of Education and Culture, 2016b, p. 6), consisting of (1) school identity, (2) subject identity, (3) class/semester, (4) material principal, (5) allocation of time, (6) learning objectives, (7) basic competencies and competency achievement indicators, (8) learning materials, (9) learning methods, (10) learning media, (11) learning resources, (12) ) learning steps; and (13) assessment of learning outcomes. The RPP is developed using the STEM approach, which theoretically can develop problem-solving skills and learning achievement. RPP has several characteristics. First, structured to improve problem-solving skills and learning achievement. It is characterized by identifying and understanding problems, exploring possible strategies, using strategies, checking and evaluating the solutions obtained. Second, When designing a car that has a high speed, it requires a front shape that can reduce friction with the air and save fuel. The amount of air friction is influenced by the coefficient of friction, the density of the air, the relative velocity of the object to the air, and the projected area of the object to the air flow. The length of the windshields of cars A and B is 60 cm, and the hood lengths of cars A and B are 70 cm. Meanwhile, the angle between the hood and the windshield of car A is 135 ° and the angle between the hood and the windshield of car B is 150 °. If the smaller the cross-sectional area, the lower the air friction. Which car has lower air friction? Table 4. Examples of learning activities in the RPP (1)

No. Teacher activities Student activities Define the Problem & Research:
18. Ask students to discuss a problem related to the sine rule, where an archaeologist is crossing a rope tied to two cliffs (STEM).
(See an example of the LKPD) Identifying the information obtained from the problem (Identifying and understanding the problem) The maximum rope tension is 7,8 × 10 2 The mass of the archaeologist is 75 kg Imagine: 19. Ask students to sketch the archaeologist's position against the rope attached to the two cliffs if the angle θ is 30°.
Students sketch the archaeologist's position against the rope attached to the two cliffs if the angle θ is 30°.
Plan: 20. Ask students how to determine the rope tension and minimum length of rope required.
Determine rope tension using the Lamy theorem. sin = sin = sin Determine the length of the rope required using the sine rule, then the result is multiplied by 2. (Exploring possible strategies) sin = sin = sin Create 21. Ask students to determine rope tension.
Determining rope tension (Using Strategy) 22. Ask students to calculate the minimum length of rope required Determine the minimum length of rope required (Using Strategy) 23. Invite students to compare the rope's condition when the rope tension angle θ is 30° with the maximum rope tension.
Answering that, what happens is the rope does not break because the tension of the rope when the angle θ is 30° is less than the maximum tension of the rope. Next, see Table 5.

Figure 1. An archaeologist is crossing a rope between two cliffs
Source: University Physics Book (Young et al., 2002) Identifying and Understanding the Problem a. What information do you get from the problems?
Exploring Possible Strategies b. Sketch the archaeologist's position against the rope attached to the two cliffs if the angle θ is 30°.
See the next page ...  in Figure 2 and Figure 3 are parallel, so that we can draw a triangle using these three vectors. Pay attention to ∆ABC Write the sine rule that applies to ∆ABC c. Write down the formula that will be used to determine the rope tension and the minimum length of rope required:

Using Strategy
d. What is the minimum rope tension and length? e. Based on the answer (d), what happened to the rope?

Checking and Evaluating the Solution Obtained
f. What is the minimum angle θ so that the rope does not break? (2 sin = ) CONCLUSION a. If the angle θ is 30°, the tension on the rope is … N and the minimum length of rope required is…. b. The minimum angle θ so that the rope does not break …°.
Are you sure all the answers are correct? Is there any other way to solve these problems? If there is, write down how here: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Description: : rope tension : weight ′ ′ ′ Jurnal Riset Pendidikan Matematika, 7 (2), 2020 -187 Aulia Nur Arivina, Jailani Furthermore, the LKPD developed uses the STEM approach with EDP steps: define the problem, research, imagine, plan, create, test and evaluate, redesign, and communicate. In defining the problem step, a problem is presented, which should be solved by the students. Research, students will collect information about the problem that may help them understand or resolve it. Imagine, students will use what they have learned to consider many possible solutions to this issue. Plan, students will choose a solution and plan for designing and resolving the problem. Create, student members will design the solution. In the test and evaluate step, the student will test and evaluate their answer to see if it successfully meets the criteria and accomplishes what it should. Redesign, if students find mistakes in the process, they may return to the "Plan" or "Create" communication. Students will share with one other and with the other teams during the lesson.

The Validity of Learning Kit
The results of the RPP and LKPD assessments of each validator shown in Table 6 and Table 7. Referring to Table 2, the two validators' average number of RPP validity scores was 140 with a good category (128 < X ≤ 144). Based on Table 6, the average score of the validity of the LKPD by the two validators was 113.5, with a good category (104 < X ≤ 117). It can be concluded that the developed RPP and LKPD was valid. Based on Table 6 and Table 7, it can be concluded that the learning kit is ready to be tested in the field with some improvements according to input from the validator. Improvements to the RPP, such as the placement of learning syntax, do not follow the learning stages, and indicators and elements of the assessment section must be written in full. While the improvement on LKPD is adding a cover to the LKPD and improving its appearance, some problems in the LKPD do not contain questions and are only in the form of important information. Based on the results of the analysis of the validity of the RPP and LKPD, it can be concluded that the trigonometry learning kit with the STEM approach to improve learning achievement and problem-solving skills is valid. It indicates that the learning kit is feasible and ready to be used for research.

The Practicality of Learning Kit
Based on Table 8, the total score of the practicality by the teacher was 93 in the very good category (85.5 < X ≤ 95), and the average score of the 32 students was 40.5 in the good category (40 < X ≤ 45). Table 9 shows that the average percentage of teacher's activities during five meetings was 87.7%, and the average percentage of students' activities during five meetings was 84.8%. The teacher and students'  responses meet the minimum good category, and the average percentage of learning implementation has reached a minimum limit of 80%. Therefore, we can conclude that the trigonometry learning kit using the STEM approach was practical.

The Effectiveness of Learning Kit
Based on Table 10, it can be seen that the increase in the mean of problem-solving skill is 67.47. Before learning using the STEM approach, no students reached it completely, but after learning using the STEM approach, 31 students reached it completely. The percentage of completeness of the problemsolving skill test has increased by 96.9%. Based on Table 10, it can be seen that the increase in the mean learning achievement is 34.06. Before learning using the STEM approach, only eight students achieved completion, but after learning using the STEM approach, 26 students reached completion. The percentage of completeness of the learning achievement test has increased by 56.25%.

Description
Problem The N-gain calculation on the learning achievement test results shows that the increase in students' achievement after learning using the STEM approach is in the moderate category. The N-gain Jurnal Riset Pendidikan Matematika, 7 (2), 2020 -189 Aulia Nur Arivina, Jailani calculation on the problem-solving skill test results shows that the increase in students' problem-solving skills after learning using the STEM approach is in the high category. Therefore, the learning kit developed to fulfill the effectiveness criteria is based on students' problem-solving skills and learning achievement.

Discussion
The trigonometry learning kit with the STEM approach is very valid, practical, and effective. It indicates that the trigonometry learning kit developed is feasible to improve problem-solving and learning achievement. The LKPD used contains motivation that inspires students to learn and provides an overview of the benefits of the material, and the problems used are everyday problems (related to science, technology, and engineering). Ahmad (2016, p. 271) states that motivation is an impetus that arises from within students to get high achievement, maintain their achievements, and direct the action to achieve their achievements. The use of everyday problems in learning activities allows students to continue to practice problem-solving (Suryaningtyas, 2017). One of the factors that affect students' difficulties in problem-solving is the lack of accuracy in working on questions (Novferma, 2016;Tias & Wustsqa, 2015). Before students conclude the answers obtained by the problem-solving process, in the developed LKPD some questions ask students to check their answers again. It aims to train students' accuracy.
With STEM, students can understand the concept of trigonometry because the learning process provides an opportunity to build mathematical concepts and relate them to real-world problems (Suherman et al., 2018, p. 7). One of the factors that affect this achievement is the use of the STEM approach. The learning kit arranged using the STEM approach invites students to learn from various disciplines. The questions in the LKPD are contextual problems related to Science, Technology, Engineering, and Math. Some of the STEM learning criteria are science and math content standards-based, gradeappropriate, and applied; students focus on solving real-world problems, and students are introduced to STEM careers and/or life applications (Jolly, 2017, p.25). In the teacher's experience, STEM learning makes students more exploratory toward a case so that the learning material becomes more meaningful for students (Arlinwibowo et al., 2020, p. 608). The questions contained in the LKPD may facilitate the problem-solving skill and learning achievement of students. Shernoff et al. (2017, p. 4) show that the benefits of implementing STEM are providing learning opportunities that are learner-centered, meaningful, interesting, and facilitating problem-solving skills. According to Moomaw (2013, p. 8), in STEM activities, teachers encourage students to solve their problems rather than give direct answers to build the knowledge they already have and deepen their conceptual understanding. Shernoff et al. (2017, p. 4) said that integrating STEM disciplines positively affects school responses and learning achievement.
The initial lesson plan is carried out face-to-face but must be carried out online because of the Covid-19 pandemic. Of course, this impacts several activities that cannot be carried out as planned, ineffective discussion activities, and less time allocation. One of the impacts is the second meeting activity, which requires students to measure the whiteboard's height when measured by two students with different elevation angles. The solution taken is to provide information about the height of two students and two elevation angles so that further activities can still be carried out. The development of lesson plans in this study has implemented several of these things. For example, starting learning by recalling the previous material and relating to the material to be studied (prerequisite), learning has been designed to be student-centered (the teacher becomes the facilitator), understanding student misconceptions by asking questions to check and evaluate the solutions obtained. The teacher trains students to work on problems by paying attention to problem-solving steps starting to identify and understand problems, check and evaluate the solutions obtained, and presenting the problems presented in students' worksheets related to real-world problems, especially those related to STEM. To support those activities, the teacher can apply several technologies (using calculators, use the internet to check the solutions).

CONCLUSION
This research's product is a trigonometry learning kit using the STEM approach to improve students' problem-solving skills and learning achievement. The learning kit has characteristics of containing learning activities that facilitate problem-solving skills and learning achievement, and the