Hi,

I've been racking my head about trying to do the following problem, but am unable to solve it:

"Quadrilateral ABCD is an isosceles trapezoid with AB parallel to CD. Find the value of P = cos(A/2) * cos(B/2) + cos(C/2) * cos(D/2)"

I started off with A+D = 180, and tried taking the sin and cos of both sides, but not sure where to continue after that.

Thanks