Question

At what angle the angle of incidence is equal to glancing angle​

Answer 1

90 degrees

Glancing angle. When dealing with a beam that is nearly parallel to a surface, it is sometimes more useful to refer to the angle between the beam and the surface, rather than that between the beam and the surface normal, in other words 90° minus the angle of incidence.

Answer 2

at 45° the angle of the incidence is equal to the glancing angle