Question

$\cos (2{\tan }^{-1}(\frac{1}{5}))=$

• A. $\frac{12}{13}$
• B. $\frac{24}{25}$
• C. $\frac{26}{25}$
• D. $\frac{13}{12}$

Answer 1

Answer: (A)

$2{\tan }^{-1}x={\cos }^{-1}\left(\frac{1-x^2}{1+x^2}\right)$