Calculation of simple Integrals



Dear All,
I am quite a newbie (I used maxima only a while several years ago),
but there is something I find a biut strange:

(%i2) integrate(sin(x), x, 0 , %pi);
(%o2)                                  2
(%i3) integrate(sin(x)^2, x, 0 , %pi);
                                      %pi
(%o3)                                 ---
                                       2
(%i4) integrate(abs(sin(x))^2, x, 0 , %pi);
                                      %pi
(%o4)                                 ---
                                       2
(%i5) integrate(abs(sin(x)), x, 0 , %pi);
                               %pi
                              /
                              [
(%o5)                         I    abs(sin(x)) dx
                              ]
                              /
                               0

So, it looks like that maxima (as expected!) has no trouble in
calculating definite integrals of simple trigonometric functions, but
if I add an absolute value, even if it has no effect on the sinus in
the selected interval, then it returns what (according to some reading
I did) stands for its inability of calculating the integral
analytically.
Why is that? Am I misunderstanding anything?
Kind Regards

Lorenzo

-- 
I went to the race track once and bet on a horse that was so good that
it took seven others to beat him!