MCQ
Write the function in the simplest form: $\tan ^{-1}\left(\frac{\cos x-\sin x}{\cos x+\sin x}\right)$
- A$-\frac{\pi}{4}+x$
- B$-\frac{\pi}{4}-x$
- ✓$\frac{\pi}{4}-x$
- D$\frac{\pi}{4}+x$
$=\tan ^{-1}\left(\frac{1-\left(\frac{\sin x}{\cos x}\right)}{1+\left(\frac{\sin x}{\cos x}\right)}\right)$
$=\tan ^{-1}\left(\frac{1-\tan x}{1+\tan x}\right)$
$=\tan ^{-1}(1)-\tan ^{-1}(\tan x)$ $\left[\because \frac{-y}{x y}=\tan ^{-1} x-\tan ^{-1} y\right]$
$=\frac{\pi}{4}-x$
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