I have to factor the expression and use fundamental identities:

Question

sins^2xcscx^2-sin^2x

sec^4x-tan^4x

Answer 1

sins^2xcscx^2-sin^2x
= sin^2x(csc^2x - 1)
= sin^2x(cot^2x)
= sin^2x(cos^2x/sin^2x)
= cos^2x

sec^4x - tan^4x
= (sec^2x - tan^2x)(sec^2x + tan^2x)
= (tan^2x + 1 - tan^2x)(tan^2x + 1 + tan^2x)
= 1(2tan^2x +1)
= 2tan^2x + 1

Answer 2

OHHH okay, THANKS!