James C. answered 01/24/21
BS in Mathematics with 20+ years of teaching experience
(cscx + cotx)(cscx - cotx) = 1
When we multiply the quantities on the left, we get...
csc2x - cot2x
Using one of the Pythagorean Identities, 1+cot2x = csc2x, we can substitute for the csc2x term...
1 + cot2x - cot2x = 1
And there you have it.