Thread: kindly help me for this proof of triangles

1. kindly help me for this proof of triangles

the question and figure is attached

2. Hi

You need to use the fact that angle $\theta$ is unchanged at reflection

Using Pythagorean theorem

$l = \sqrt{(h_t-h_r)^2+d^2}$

$x + x' = \sqrt{(h_t+h_r)^2+d^2}$