A pyramid MABCD with the top-vertex M is circumscribed about a sphere with center O so that O lies on the altitude of the pyramid. Each of the planes ACM,BDM,ABO divides the lateral surface of the pyramid into two parts of equal areas. The areas of the sections of the planes ACM and ABO inside the pyramid are in ratio (2+2):4. Determine the angle δ between the planes ACM and ABO, and the dihedral angle of the pyramid at the edge AB. geometry3D geometrypyramidarea