Thanks for the help! If you could please show all your work? Thanks again!
Kirill and Felice gave good answers, but I wanted to add this to eliminate any confusion.
We can only use trig functions with right triangles, so you have to use Pythagorean's Theorem to solve for the hypotenuse: a2+b2=c2. a and b = 4 and 11, in either order, according to the problem. Therefore, c2=137; c=sqrt137.
I hope that fills in any gaps. Kirill and Felice covered the rest of the explanation.