PdP=(-32siny*cos^3(y))*dcosy/-siny
PdP=(-32sinycos^3(y)*dcosy)/-siny
P^2/2=32cos^3(y)dcosy
P^2=2*32*cos^4(y)/4
P^2=16cos^4(y)
P=4*cos^2(y)