What is the relationship between the reflection angles in a prism?

[shyta]

Homework Statement

For a beam of light shone on a prism, the reflected beams will give twice the angle of the prism.

Homework Equations

We know that the angle between the incident ray and the normal = angle between reflected ray and normal

The Attempt at a Solution

i tried drawing a diagram but couldn't find a solution

 

[rl.bhat]

Let ABC be an equilateral or isosceles prism with A as angle of prism.
Let a parallel beam PQ and RS incident on the face AB and AC respectively.
QM and SN are the reflected rays from the respective faces. Draw AD perpendicular to BC.
Let MQ and NS meet at E which lies on AD.
Applying laws of reflection, you can see that AQ is the angle bisector of PQE.
Now can you draw the diagram and proceed?