Question #46824

1 Answer
Oct 15, 2017

90°

Explanation:

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We know that the reflected ray from the mirror, the mirror and the horizontal will make a triangle.

Sum of angles of a triangle =180°

Let's call that triangle ∆ABC

We know that A= theta

As angle i =theta, angler=theta

And, angler +angleABC=90°
[With the normal]

therefore angle ABC+theta=90°
=>angleABC=90°-theta---(1)

angle ABC + theta + angle BCA = 180°

We want to find angleBCA.

So, angle BCA = 180°-(theta+angleABC)

Substituting from (1),
angle BCA = 180°-(cancel(theta)+90cancel(-theta))

therefore angleBCA=180-90=90°

Since angleBCA=90°, the angle between the reflected ray and the horizontal would be 90°