Hook Consider allowing students to explore a resource that restricts examples to right angle triangles. At the end of the exploration illicit that there are other kinds of triangles (oblique) that we need to be able to calculate angle and side values for. Lesson Goal Students can see the relationship between angles and the length of opposite sides and use the sine law to find unknown sides and angle measures. Students will realize that sine law can be used when a triangle does not have a 90º angle, but an angle, its opposite side, and at least one other angle or side is known. Activate Prior Knowledge Students will be using a protractor to determine angle size(s) and a ruler to determine side length(s). They will need to set up a ratio using appropriate sides and angles. Lesson Discuss the relationship between the sine of the angle and the opposite side. Teach the sine law to show how this relationship can be used to find unknown sides and angles. Stress to students that the sine law can only be used if you are given (or can find) the angle, its opposite side, and at least one other angle or side. Go through examples finding: unknown sides unknown angles. Provide examples to be given where sine law must be used to solve triangles. Problems should include examples where students must sketch a diagram and solve a problem using the sine law. Going Beyond Resources Math 20-1 (McGraw-Hill Ryerson: sec 2.3, pages 100-113)
Hook Consider allowing students to explore a resource that restricts examples to right angle triangles. At the end of the exploration illicit that there are other kinds of triangles (oblique) that we need to be able to calculate angle and side values for. Lesson Goal Students can see the relationship between angles and the length of opposite sides and use the sine law to find unknown sides and angle measures. Students will realize that sine law can be used when a triangle does not have a 90º angle, but an angle, its opposite side, and at least one other angle or side is known. Activate Prior Knowledge Students will be using a protractor to determine angle size(s) and a ruler to determine side length(s). They will need to set up a ratio using appropriate sides and angles. Lesson Discuss the relationship between the sine of the angle and the opposite side. Teach the sine law to show how this relationship can be used to find unknown sides and angles. Stress to students that the sine law can only be used if you are given (or can find) the angle, its opposite side, and at least one other angle or side. Go through examples finding: unknown sides unknown angles. Provide examples to be given where sine law must be used to solve triangles. Problems should include examples where students must sketch a diagram and solve a problem using the sine law. Going Beyond Resources Math 20-1 (McGraw-Hill Ryerson: sec 2.3, pages 100-113)