Question

Can somone please help me?

Answer 1

\[a\text{=}\text{ArcTan}\left[\frac{2}{x}\right] \]\[\left(\frac{\pi }{2}-a\right)=\text{ArcTan}\left[\frac{10}{x}\right]\]\[\frac{\pi }{2}-\text{ArcTan}\left[\frac{2}{x}\right]=\text{ArcTan}\left[\frac{10}{x}\right]\]\[x=2 \sqrt{5} \]