4.2. Write a function trap (f, a, b, n) that computes the trapezoidal rule ap- proximation to Sa f (x)dx, f(x0) +2 f (xi) +2f (x2)+...+2 f (xn-1) + f (xn)], where h = (b a) and xi = a +ih. Test your function on sin(x) + cos(x) for 0