The way to find the length of one side of a triangle can be to use SOHCAHTOA, an abbreviation learnt to help rememeber the process. SOH stands for sin = opposite / hypotenuse , CAH stands for cos = adjacent / hypotenuse and TOA stands for tan = opposite over adjacent. The angle of the triangle provided should be used to determine whether sin, cos or tan will be used for this particular triangle. Once this has been completed, for example if you were using sin, the formula would be sin (angle provided) = length of opposite side / length of hypotenuse side.