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Let $ABCD$ be a square with side length $1.$ A laser is located at vertex $A,$ which fires a laser beam at point $X$ on side $\overline{BC},$ such that $BX = \frac{1}{2}.$  The beam reflects off the sides of the square, until it ends up at another vertex; at this point, the beam will stop.  Find the length of the total path of the laser beam.

 Aug 22, 2024
 #1
avatar+1926 
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Look at the graph attached below. 

 

The ray will strike X and then, because angle A = angle B  it will travel to vertex D

 

Thus, the total path legnth is 

\(2 \sqrt {0 .5^2  + 1^2 } =  2 \sqrt { 5/4}  = \sqrt 5\)

 

Thanks! :)

 Aug 22, 2024
edited by NotThatSmart  Aug 22, 2024

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