Prove the identity of: 1+tan^2 x = 1/cos^2 x

Answer 1

1 + tan^2x = 1/cos^2x

1+ tan^2x = sec^2x is a standard trig identity

or

1 + sin^2x/cos^2x = 1/cos^2x multiply both sides by cos^2x to get

cos^2x + sin^2x = 1 which is a version of the Pythagorean Theorem x^2 + y^2 = 1^2 for a unit circle