Year 9 Trigonometry (Finding Sides) Worksheet — Level 2 — Practice Set 4 — Answers
Answer sheet with worked solutions for the Year 9 trigonometry worksheet.
Year 9 Trigonometry (Finding Sides) Worksheet — Level 2 — Practice Set 4 — Answers
Label the sides (opposite, adjacent, hypotenuse), choose the ratio (SOH CAH TOA), then solve.
1.In a right-angled triangle, the hypotenuse is 5 cm and one angle is 24°. Find the side adjacent to the 24° angle, to 1 decimal place.
Answer: 4.6 cm
- cos 24° = adjacent ÷ hypotenuse
- adjacent = 5 × cos 24°
- ≈ 4.6
2.In a right-angled triangle, the hypotenuse is 8 cm and one angle is 33°. Find the side adjacent to the 33° angle, to 1 decimal place.
Answer: 6.7 cm
- cos 33° = adjacent ÷ hypotenuse
- adjacent = 8 × cos 33°
- ≈ 6.7
3.In a right-angled triangle, the side adjacent to a 49° angle is 11 m. Find the opposite side, to 1 decimal place.
Answer: 12.7 m
- tan 49° = opposite ÷ adjacent
- opposite = 11 × tan 49°
- ≈ 12.7
4.In a right-angled triangle, the hypotenuse is 8 cm and one angle is 41°. Find the side adjacent to the 41° angle, to 1 decimal place.
Answer: 6 cm
- cos 41° = adjacent ÷ hypotenuse
- adjacent = 8 × cos 41°
- ≈ 6
5.In a right-angled triangle, the hypotenuse is 19 cm and one angle is 53°. Find the side adjacent to the 53° angle, to 1 decimal place.
Answer: 11.4 cm
- cos 53° = adjacent ÷ hypotenuse
- adjacent = 19 × cos 53°
- ≈ 11.4
6.In a right-angled triangle, the hypotenuse is 16 cm and one angle is 64°. Find the side opposite the 64° angle, to 1 decimal place.
Answer: 14.4 cm
- sin 64° = opposite ÷ hypotenuse
- opposite = 16 × sin 64°
- ≈ 14.4
7.In a right-angled triangle, the side adjacent to a 20° angle is 13 m. Find the opposite side, to 1 decimal place.
Answer: 4.7 m
- tan 20° = opposite ÷ adjacent
- opposite = 13 × tan 20°
- ≈ 4.7
8.In a right-angled triangle, the hypotenuse is 15 cm and one angle is 64°. Find the side opposite the 64° angle, to 1 decimal place.
Answer: 13.5 cm
- sin 64° = opposite ÷ hypotenuse
- opposite = 15 × sin 64°
- ≈ 13.5
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
- For open-ended tasks, use the success criteria as a checklist rather than looking for one "right" answer.
- Celebrate what went well first, then pick one thing to work on next.
Great work. Here's what to try next: