MCQ
If $4 \sin ^{-1} x+6 \cos ^{-1} x=3 \pi$ then $x=$
  • A
    $1 / \sqrt{2}$
  • B
    $1 / 2$
  • 0
  • D
    $-1 / 2$

Answer

Correct option: C.
0
(c) : $4 \sin ^{-1} x+6 \cos ^{-1} x=3 \pi$
$
\begin{gathered}
\Rightarrow 4 \sin ^{-1} x+6\left(\frac{\pi}{2}-\sin ^{-1} x\right)=3 \pi \\
{\left[\because \sin ^{-1} x+\cos ^{-1} x=\frac{\pi}{2}\right]} \\
\Rightarrow 4 \sin ^{-1} x+3 \pi-6 \sin ^{-1} x=3 \pi \\
\Rightarrow-2 \sin ^{-1} x=0 \Rightarrow \sin ^{-1} x=0 \Rightarrow x=0
\end{gathered}
$

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