Hi everyone.
Recently, I came across a closed form solution to ∫|cos(x)|dx as
sin(x-∏*floor(x/∏+1/2)) + 2*floor(x/∏+1/2)
I have no idea how to reach this solution but checking this for definite integral from 0 to 3∏/4 or ∏ seems to work. Using |cos(x)| as cos(x)*sgn(cos(x)) doesn't...