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Home > CCG > Chapter 7 > Lesson 7.2.2 > Problem 7-67


A light directed from point is pointed at a hinged mirror with right angle as shown at right.  

  1. If measures , find the measures of , , , , and .

    When the light hits the mirror the angle of incidence and angle of reflection are congruent. Therefore 

    , , ,

  2. Why must the arrows at points and be parallel?

    Use the angle measurements found to explain why the arrows at points and must be parallel.

An entry light ray hits one mirror side through point E at an angle, x, to the mirror side. It bounces off to the opposite corner side with an angle, z, between the entry ray, and bounce ray, and angle a, between the mirror side and bounce ray. It bounces off again, creating an exit ray away from the mirror passing through point A, leaving 3 angles, r, between the mirror side and the bounce ray, y, between  bounce ray and exit ray, and m, between the mirror and exit ray.