Number

Statistics and Probability

Algebra

4.5 Trigonometry

For the following right-angled triangles calculate the unknown angle $θ$ to 1dp.

1.
$tan⁡(θ) = Opp Adj tan⁡(θ) = 5 6 θ = tan⁡ −1 ( 5 6 ) θ = 39.8°$
2.
$sin⁡(θ) = Opp Hyp sin⁡(θ) = 10 15 θ = sin⁡ −1 ( 10 15 ) θ = 41.8°$
3.
$cos⁡(θ) = Adj Hyp cos⁡(θ) = 10 15 θ = cos⁡ −1 ( 10 15 ) θ = 48.2°$

## Remember the SOHCAHTOA mnemonic

Remember the names of the sides of a right-angled triangle and apply ‘SOHCAHTOA’ to calculate the unknown angle.