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Q. The value of $\sin (2\, \sin^{-1}\, 0.8)$ is equal to

KCETKCET 2014Inverse Trigonometric Functions

Solution:

Let $E =\sin \left(2 \sin ^{-1} 0.8\right)$
Put $\sin ^{-1} 0.8=\theta$
$\Rightarrow \sin \theta=0.8$
$\therefore \cos \theta =\sqrt{1-\sin ^{2} \theta}$
$=\sqrt{1-0.64}=\sqrt{0.36}=0.6$
$\therefore E =\sin (2 \theta)=2 \sin \theta \cos \theta$
$=2 \times 0.8 \times 0.6=0.96$