Ikind of know how to do these problems, but im stuck on this one right now. prove the formula below

Use difference of squares. (I'm leaving out the "x" part)

csc^4 - cot^4 = (csc^2 + cot^2)(csc^2 - cot^2)

From here, we should recognize one of the trig identities:

1 + cot^2 = csc^2
or rewritten as:
1 = csc^2-cot^2

So we can substitute the above into our previous equation:
(csc^2 + cot^2)(csc^2 - cot^2)
= (csc^2 + cot^2)(1)
= csc^2 + cot^2

And we have proven it. :)

Ithink it is b and d