Angle between two planes

General equation OF plane || Vector form OF plane || Parametric form OF plane || Image OF a point line in a plane || Normal form OF plane || Angle between two plane

Bond angle between two plane in crystalline state of H_(2)O_(2) is _________.

Bond angle between two plane in crystalline state of H_(2)O_(2) is _________.

What should be the angle between two plane mirrorrs so that whatever be the angle of incidence, the incident ray and the reflected ray from the two mirrorrs be parallel to each other