Question:
Solve: $\cos \left(\sin ^{-1} x\right)=\frac{1}{6}$
Solution:
$\cos \left(\sin ^{-1} x\right)=\frac{1}{6}$
$\Rightarrow \cos \left(\cos ^{-1} \sqrt{1-x^{2}}\right)=\frac{1}{6}$
$\Rightarrow \sqrt{1-x^{2}}=\frac{1}{6}$
$\Rightarrow 1-x^{2}=\frac{1}{36}$
$\Rightarrow 1-\frac{1}{36}=x^{2}$
$\Rightarrow x^{2}=\frac{35}{36}$
$\Rightarrow x=\pm \frac{\sqrt{35}}{6}$