Trying to integrate the following

([ will stand for the integral sign)

[|cos(x)|^3 dx between 0 and 2pi

Now, Maple tells me the answer should be 8/3, but I keep getting 0.

[|cos(x)|^3 dx = [cos^2(x).cos(x) dx

= [(1-sin^2(x)].cos(x)dx

= [cos(x)-cos(x)sin^2(x) dx

= sin(x) -sin^3/3

which gives me 0 when I evaluate it. Any help would really be appreciated. Thank you