you can factor the left side of the equation to
(csc^2 + cot^2)(csc^2 - cot^2)
then, since cot^2 + 1 = csc^2, you can replace the csc^2 in the left parentheses with cot^2 + 1, and the cot^2 in the right parentheses with csc^2 - 1 (which equals cot^2)
then, youll end up with
(cot^2 + 1 - cot^2)(csc^2 + csc^2 - 1)
combine like terms, and the left parentheses becomes 1 (cot^2 - cot^2 = 0), and the right parentheses becomes 2csc^2 - 1.
1(2csc^2 - 1) = 2csc^2 - 1
