Question

Decide whether the equations is a trigonometric function identity, EXPLAIN.

Answer 1

(1) Answer: Identity true

$\cos^2x(1+\tan^2x)=\cos^2x(1+\frac{sin^2x}{cos^2x})=\\= \cos^2x\frac{cos^2x+sin^2x}{cos^2x}=1$

(2) Answer: Identity true

$\sec x \tan x(1-\sin^2x)=\sin x\\\frac{1}{\cos x}\frac{\sin x}{\cos x}(\cos^2x)=\sin x\\\sin x = \sin x$

(3) Answer: Identity true

$\sin^2(\theta)\csc^2(\theta)=\sin^2(\theta)+\cos^2(\theta)\\\sin^2(\theta)\frac{1}{\sin^2(\theta)}=\sin^2(\theta)+\cos^2(\theta)\\1 = 1$