MathDB

The sides of a

10

10

square

ABCD

are reflective on the inside. A beam of light enters the square via the vertex

A

and heads to the point

P

CD

with

CP = 3

and

PD = 7

. In

P

it naturally reflects on the

CD

side. The light beam can only leave the square via one of the angular points

A, B, C

D

. What is the distance that the light beam travels within the square before it leaves the square again? By which vertex does that happen?

Problem Statement