Error when integrating absolute value

[pinkman]

(12-06-2019 08:42 PM)parisse Wrote:  Please read the whole warning. The problem comes from singulatiries in sign(cos(variable_name)) inside the antiderivative.

Hi Bernard, thanks for trying to help us, but I’m really confused or puzzled by your answer that I don’t understand.
I know the problem of the singularities, but for me there is no doubt that ∫(ABS(cos(x)),x,-π/2,3*π/2) = 4, and ∫(k*ABS(cos(x)),x,-π/2,3*π/2) = k*4 in the real domain, k being a constant.

Am I wrong?