Question

the angle between a flashlight beam that strikes a mirror and the reflected beam is 80 degrees. What is the angle of incidence?

Answer 1

Since the angle of incidence and reflection are equal and the sum of them span the incident and reflected beam (80 degrees) then the angle of incidence is 40 degrees.  This makes the sum of incident and reflected angles (which are the same) 40+40=80

Answer 2

Answer:

Angle of incidence is equal to $40$ degrees

Explanation:

There are two angles between the striking and reflected beam , namely angle of incidence and reflection

Sum of angle of incidence "I" and angle of reflection "R" is equal to $80$ degrees

$I + R = 80\\I = R\\I + I = 80\\I = 40$

Thus angle of incidence is equal to $40$ degrees