Max RANGE of a projectile thrown from the top of a ramp.

[VyRianS]

Homework Statement

A projectile is thrown from the top of the ramp. Find the angle $\theta$ of the throw that gives a max range R down the ramp. $\phi$ is the angle made from the base of the ramp to the x-axis.

2. The attempt at a solution

Tried a number of times but failed to get anything that seemed moderately appropriate, i.e. getting long equations that are obviously too complex to be the answer.

Appreciate the help.

Thanks.

 

[Punkyc7]

Did you use a trig identity to simplify it?