Trigonometry identity

Question

(1 - cos^2 A) (1 + cot^2 A) = 1

Answer 1

In order to solve this you need to know the basics.

CotA = cosA/sinA

Sin^2 A + cos^2 A = 1

Use both and you'll get it solved

Answer 2

Each of the two factors on the left are part of a Pythagorean Identity.

Convert and simplifey.