## Algebra and Trigonometry 10th Edition

$cot(arctan~x)=\frac{1}{x}$
Let $u=arctan~x~~$ (Range: $-\frac{\pi}{2}\lt u\lt\frac{\pi}{2}$) Then: $x=tan~u$ $cot(arctan~x)=cot~u=\frac{1}{tan~u}=\frac{1}{x}$