2sec^2x-2sec^2xsin^2x-sin^2x-cos^2x=1
Help??

First convert secant functions to cosine equivalents.

Next - divide the 2/cos^2x term out of the first two terms.

Lastly - remember the identity cos^2x + sin^2x = 1, and its variant 1-sin^2x + cos^2x.

Post back and show us your work if you're still having difficulty.