Question:
Mark the tick against the correct answer in the following:
$\sin \left[2 \sin ^{-1} \frac{4}{5}\right]$
A. $\frac{12}{25}$
B. $\frac{16}{25}$
C. $\frac{24}{25}$
D. None of these
Solution:
To Find: The value of $\sin \left(2 \sin ^{-1} \frac{4}{5}\right)$
Let, $x=\sin ^{-1} \frac{4}{5}$
$\Rightarrow \sin x=\frac{4}{5}$
We know that, $\cos x=\sqrt{1-\sin ^{2} x}$
$=\sqrt{1-\left(\frac{4}{5}\right)^{2}}$
$=\frac{3}{5}$
Now since, $x=\sin ^{-1} \frac{4}{5}$, hence $\sin \left(2 \sin ^{-1} \frac{4}{5}\right)$ becomes $\sin (2 x)$
Here, $\sin (2 x)=2 \sin x \cos x$
$=2 \times \frac{4}{5} \times \frac{3}{5}$
$=\frac{24}{25}$