How do you find the length of a side of a right-angled triangle given the angle and the hypotenuse?

First label the triangle to show the opposite, adjacent and hypotenuse. Then you can use SOHCAHTOA to determine which trig function is needed. If you need to work out the opposite you use the sin function and if you need to work out the adjacent you use the cos function. as sin(angle) = opposite/hypotenuse then opposite = sin(angle) x hypotenuse. as cos(angle) = opposite/hypotenuse then opposite = cos(angle) x hypotenuse.