#### Sonicdude41

##### Senior Member

Here is the original problem:

From here, I changed sec^2(x) - 1 to tanx because one of the Pythagorean Identities, when you fiddle with it, makes this true, as shown below.

I then proceeded to change tan^2(x) to sin^2(x)/cos^2(x), since that is another identity that is true. The same also applies to secx, except it was changed to 1/cosx.

After that, I'm stuck. Any ideas?