I am not understanding at all how to do the trigonometric identities...

As far as i know we had 12 of them that we had to memorize, even after memorizing them i am unsure of how to apply them.

so for my first question the problem says

(sinx + cosx)(sinx + cosx) -1 / sinxcosx

multiply and simplify

the answer is 2 however im unsure how you get that answer.

also there is

1 + tan^2(-x) = sec^2(x)

how do I get both sides to equal the same im suppose to use the more complicated side, but, which identity do I use?

If there is any easy way to remember the identities and to apply them that would be great..

thanks in advance