Question

Prove that: 1-tan^2a / 1+ tan^2a = cos^2a-1/cos^2a+1

Answer 1

Step-by-step explanation:

cos2A = cos^2 A - sin^2 A

= cos^2 A ( 1 - tan^2 A)

= (1 - tan^2 A)/sec^2 A

= (1 - tan^2 A)/(1 + tan^2 A)