Question

cos to the power -1 (2x/1+x to the power 2) solve it and proof cos

Answer 1

$\cos { }^{ - 1} ( \frac{2x}{1 + {x}^{2} } )$

$= \cos {}^{ - 1} ( \frac{2 tan \alpha }{1 + tan {}^{2} \alpha } )$

where x=tan@

$= \cos {}^{ - 1} ( \cos2 \alpha )$

$= 2 \alpha$

$= 2 \tan {}^{ - 1} (x)$