Relation between mirror angle and light ray deflection angle

[PintoCorreia]

Homework Statement

It turns out there is a relation between angle a and angle b. I can't figure it out, could someone give me a hint?

There's a lightray that is bouncing from two mirrors (m1 and m2).

The angle between those two mirrors is called a.

The angle between the incoming lightray l1 and the mirror m1 is called x.

The angle between the incoming lightray l1 and the outgoing lightray l3 called b.

Homework Equations

incoming angle it outgoing angle

The Attempt at a Solution

I get stuck at the mathematical proof... Someone a clue?

 

[Tanya Sharma]

What are the given parameters ? Is 'x' a given quantity or some angle assumed by you ?

Look at the figure I have attached .Blue lines are normal lines to the two mirrors respectively.

What is ∠BAC in terms of x ?