3. (25 pts) Use Euler's , Midpoint, Heun's methods with h-1, h=0.5 and h=0.25 to approximate y(2.1) where y(t) is the solution of the initial value problem n1:3 n2:38 0138t dy %3D s(), y(0.1)-0.81 * Cos dt find the relative error in y(2.1) for each step length.