Definition:
The Planes 1 and Plane 2 intersect at straight line CD.
If both line l and line n are perpendicular to CD,
then angle C2 is the angle bewteen Planes 1 and Plane 2.
2025_05_16_Angles between two retangular planes (The point "P" and "C2" are able to move)
2025_05_16_Angles between two planes that are not retangles