Hint
Use the stated units and precision. Use the parallel-line co-interior angle sum.
Worked solution
(a)
Use the parallel-line co-interior angle sum.
Co-interior angles sum to 180°, giving 125°.
Answer: \(125\)
(b)
Use corresponding angles rather than a supplementary-angle rule.
Corresponding angles on parallel lines are equal, so the angle is 55°.
Answer: \(55\)
(c)
Subtract the two known angles from the triangle angle sum.
The triangle sum gives \(\displaystyle 180-55-37=88\)°.
Answer: \(88\)
Maths4U indicative marking guidance
Maths4U indicative marking guidance, not an official mark scheme. Credit complete valid alternative methods and consequential reasoning. An unexplained result does not earn a method mark.
(a) · 2 marks
- 1 mark: Use the parallel-line co-interior angle sum.
- 1 mark: Give the correct requested result, retaining signs, units and any domain restrictions.
Alternative methods: Any complete mathematically valid alternative method with the same restrictions and equivalent exact result is acceptable.
Common error: Keep intermediate values exact until the final step.
(b) · 2 marks
- 1 mark: Use corresponding angles rather than a supplementary-angle rule.
- 1 mark: Give the correct requested result, retaining signs, units and any domain restrictions.
Alternative methods: Any complete mathematically valid alternative method with the same restrictions and equivalent exact result is acceptable.
Common error: Check the answer against the original conditions.
(c) · 2 marks
- 1 mark: Subtract the two known angles from the triangle angle sum.
- 1 mark: Give the correct requested result, retaining signs, units and any domain restrictions.
Alternative methods: Any complete mathematically valid alternative method with the same restrictions and equivalent exact result is acceptable.
Common error: Keep intermediate values exact until the final step.
Total: 6 marks.