Question

Verify the identity. Show your work. (1 + tan^2u)(1 - sin^2u) = 1

Answer 1

$\bf \textit{Pythagorean Identities} \\\\ sin^2(\theta)+cos^2(\theta)=1\implies cos^2(\theta)=1-sin^2(\theta) \\\\ 1+tan^2(\theta)=sec^2(\theta)\\\\ -------------------------------\\\\\ [1+tan^2(u)][1-sin^2(u)]=1 \\\\\\\ [sec^2(u)][cos^2(u)]\implies \cfrac{1}{cos^2(u)}\cdot cos^2(u)\implies \cfrac{cos^2(u)}{cos^2(u)}\implies 1$