Question

prove that the above question​

Answer 1

tan = sin / cos Therefore, tan^ 2 = sin^2 / cos^2

The right hand side

(1- tan^2) / (1 + tan^2) = (1 - sin^2 / cos^2) / (1 + sin^2 / cos^2)

Multiplying both top and bottom by cos ^2,

= (cos^2 - sin^2) / (cos^2 + sin^2)

But cos^2 + sin^2 = 1, which means it is equal to

(cos^2 - sin^2), which is equal to the left side of the equation.