How do we calculate the Max value of x?

[osy044]

Homework Statement

where

x=(4aV^2tan$$\alpha$$)/(V^2+2ag+2agtan^2$$\alpha$$)

where a, V, g are constant. g is gravitational field strangth.
what is the greatest value of x as $$\alpha$$ varies?

how do i even start?

Homework Equations

The Attempt at a Solution

 

[vela]

How do you usually find the maximum of a function?