At GCSE it's easiest just to use a calculator to find sin, cos and tan of an angle. Just make sure it is set to the right mode(probably only degrees for GCSE).
Sin(angle) = opposite / hypotenuse
Cos(angle) = adjacent / hypotenuse
Tan (angle) = opposite / adjacent
Posted from TSR Mobile
SOH = Sin theta = Opposite/Hypotenuse
CAH = Cos theta = Adjacent/Hypotenuse
TOA = Tan theta = Opposite/Adjacent