Plug into the Sine subtraction formula which is sin(x - y) = sinxcosy - cosxsiny So First find the Cos of the values using a triangle and the Pythagorean theorem Triangle X missing side =Sqrt(5^2 - 4^2) = 3 Triangle y missing side = sqrt(13^2 - 12^2) = 5 So we now plug it into the equation (4/5)(5/13) - (3/5)(12/13) Multiply 4/13 - 36/65 = -16/65