How can I solve a 2D motion problem with angles and components?

[moondawg]

Homework Statement

In class we had a 2D with angles and components question.

Homework Equations

To find the answer I eventually got to the x=xo+v_ot+1/2at² equation and came up with ***-4.9(28/37cosx)²+28tanx-3***

The Attempt at a Solution

But once I got to this point I did not know how to solve it. I would think to plug it into the quadratic formula but how can i do that if my supposed x and x² values are not the same? One has a coefficient and cosx and the next is tanx. My teahcer plugged it into his advanced(/cheater) calculator and got x=11.9 degrees which is the right answer but i do not have that kind of calculator and do not know where to go from the equation above.
Please help!

 

[Doc Al]

Hint: Using one of the Pythagorean Trig Identities (look them up!) you can express 1/cos²x = sec²x in terms of tanx.