√(4x^2+25) then 2 x=5tanθ
I do not understand the question either. I think something is missing.
Your question isn't clear as to you want,
If we take the sqrt of the 1st. part, then we have 2x +5,
Then you have 2x=5tan(Theta),
x=5tan(Theta)/2=2 1/2tan(Theta)