Question Working Answer Mark AO Notes Grade 1 a i No B1 2 B ii Yes B1 iii Yes B1 iv No B1 b i Assume third angle is 90°. 180° 90° = C1 C1 for full explanation – 90°. So both the remaining angles must C1 C1 for clarity of explanation be acute. If the third angle is bigger than 90° both remaining must also be acute. If the third angle is acute you would need to make one of the other angles at least 90°. ii Example with 2 acute angles. B1 B1 for giving an example that works iii Example with 1 obtuse angle. B1 B1 for giving an example that works iv C1 C1 for a correct explanation The obtuse angles will be (90° + and x) C1 C1 for clear communication (90° + adding these together you get y), 180° + + which is more than the x y, sum of the angles in a triangle, so it’s impossible. c C1 C1 for clear explanation If you draw a line between two parallel C1 C1 for clarity of the communication lines, the two allied angles formed add up to 180°, which leaves nothing for a 12 third angle.
Question Working Answer Mark AO Notes Grade 1 a i ii iii iv b i ii iii iv c No Yes Yes No Assume third angle is 90°. 180° – 90° = 90°. So both the remaining angles must be acute. If the third angle is bigger than 90° both remaining must also be acute. If the third angle is acute you would need to make one of the other angles at least 90°. Example with 2 acute angles. Example with 1 obtuse angle. The obtuse angles will be (90° + x) and (90° + y), adding these together you get 180° + x + y, which is more than the sum of the angles in a triangle, so it’s impossible. If you draw a line between two parallel lines, the two allied angles formed add up to 180°, which leaves nothing for a third angle. B1 B1 B1 B1 C1 C1 B1 B1 C1 C1 C1 C1 2 C1 for full explanation C1 for clarity of explanation B1 for giving an example that works B1 for giving an example that works C1 for a correct explanation C1 for clear communication C1 for clear explanation C1 for clarity of the communication B 12
Higher_Skills_Geometry_MarkScheme_Edexcel.docx