I have a rectangle (side length L1 and L2) and two parallel lines passing through two opposite angles:
(sorry the image is missing due to stackexchange policy)
I know that the (perpendicular) distance between the parallel lines is h, and that each line form a right triangle with the sides of the rectangle (let's say L1 is the base of such triangle).
What is the formula to calculate the angles (alpha, beta) of this right triangle?