∫ (0→π) |cosx | dx
=∫ (0→π/2) |cosx | dx+∫ (π/2→π) |cosx | dx
=∫ (0→π/2) cosx dx-∫ (π/2→π) cosx dx
=sinx |(0→π/2)- sinx |(π/2→π)
=(1-0)-(0-1)
=2