Question

tg^2a-1/tg^2a+1 +cos^2a

Answer 1

$mathtt{frac{tg^2a-1}{tg^2a+1}+cos^2a=frac{frac{sin^2a}{cos^2a}-1}{frac{sin^2a}{cos^2a}+1}+cos^2a=frac{frac{sin^2a}{cos^2a}-frac{cos^2a}{cos^2a}}{frac{sin^2a}{cos^2a}+frac{cos^2a}{cos^2a}}+cos^2a=frac{frac{sin^2a-cos^2a}{cos^2a}}{frac{sin^2a+cos^2a}{cos^2a}}+}\mathtt{cos^2a=frac{sin^2a-cos^2a}{sin^2a+cos^2a}+cos^2a=sin^2a-cos^2a+cos^2a=sin^2a}$