Trigonometric ratios connect the angles and sides of a right-angled triangle.
The three ratios
$\sin\theta = \dfrac{\text{opposite}}{\text{hypotenuse}}$ · $\cos\theta = \dfrac{\text{adjacent}}{\text{hypotenuse}}$ · $\tan\theta = \dfrac{\text{opposite}}{\text{adjacent}}$
For a triangle with opposite 3, adjacent 4 and hypotenuse 5: $\sin\theta = \tfrac{3}{5} = 0.6$ and $\tan\theta = \tfrac{3}{4} = 0.75$.
Remember
- SOH-CAH-TOA: Sin=O/H, Cos=A/H, Tan=O/A.
- The hypotenuse is the longest side.