Q. The value of $\cos{(2\cos^{- 1}{0.8})}$ is
A) 0.48
B) 0.96
C) 0.6
D) None of these
Explanation
(d)
Since, $2\cos^{- 1}{x = \cos^{- 1}{(2x^{2} - 1)}}$
Therefore,
$2\cos^{- 1}{0.8 = \cos^{- 1}{(2 \times 0.64 - 1) = \cos^{- 1}{(0.28)}}}$
$\Rightarrow \ \cos{(2cos^{- 1}0.8)} = \cos{\left( \cos^{- 1}{0.28} \right) = 0.28}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.