Trigonometry: sin, cos and tan
Learn Trigonometry: sin, cos and tan for Years 9–11 pupils (ages 13–16). Free practice questions, lessons and worked examples — aligned to the UK National Curriculum.
What you'll learn
- 1
In a right-angled triangle: sin = opposite/hypotenuse, cos = adjacent/hypotenuse, tan = opposite/adjacent.
- 2
The hypotenuse is always the longest side, opposite the right angle. Opposite and adjacent depend on which angle you are using.
- 3
Which ratio uses opposite and adjacent?
- 4
These ratios only work in RIGHT-ANGLED triangles. Without a right angle you need the sine or cosine rule instead.
- 5
A right-angled triangle has hypotenuse 10 cm and an angle of 30°. The opposite side = 10 × sin(30°) = 10 × 0.5 = 5 cm.
- 6
To find the opposite side given the hypotenuse and an angle, which ratio?
- 7
When can you use Pythagoras instead of trigonometry?
Practise Trigonometry: sin, cos and tan with Whizlo
Free AI-tutored lessons, unlimited practice questions, and progress tracking for ages 13–16. Aligned to the UK National Curriculum.