Solving a Trigonometry Problem: Need Help!

[intervade]

So I'm not really sure how to go about this problem. I've attempted letting x = a few things. 4sinx, and 4tanx. Maybe trig substitution is not even the way to go. Could someone push me in the right direction?

 

[rock.freak667]

Yes x=2tanθ should work. Try it out and post back if you do not get through.