Verifying identities

We have different identities to deal with the trig formulas, and those identities makes it easier to solve. For example, sin^2x+cos^2x=1, and 1+tan^2x=sec^2x. In order to solve the problem completely, we should use some rules, first simplify more complicated side. Second, we should find their common denominators if it is possible. We should always change all trig function in terms of sine and cosine. And finally, we can try to plug them into the identities we learned this week.