∫[cos(ωx+Ψ)]^2dx
=(1/2)∫[1+cos2(ωx+Ψ)]dx
=(1/2)∫dx+[1/(4ω)]∫cos2(ωx+Ψ)d[2(ωx+Ψ)]
=(1/2)∫dx+[1/(4ω)]sin2(ωx+Ψ)+C.