Eek, its better to just use LaTex (if you know how) and link the problem.

However this isn't a "simple" integral, unless you are familiar with trig substitutions. Lets do a little bit of math trickery:

Thus:

From here we simplify:

This integral is easy to evaluate:

However, we need our final answer in terms of x, not theta. So, we go back to our original substitution:

. . .and solve for theta. Do not "memorize" formulas or "tricks" (this really isn't a trick though I called it so) - memorize (or KNOW) identities, and familiar algebraic structures.