Question

write the expression in terms of sin and cosine, simply so that no quotients appear in the final expression
sin^2x-1/cos(-x)

Answer 1

well if you start with

sin^2 +cos^2 = 1

then cos^2 = 1 - sin^2

or

cos^2 = -1(sin^2 -1)

so

-cos^2 = sin^2 - 1

make the substitution....

and isn't

cos(-x) the same as -cos(x)

make that substitution...

and it should be easy to simplify now.