$\dfrac{d}{dx}(\sin^{-1} x)$ equals:
- $\dfrac{-1}{\sqrt{1-x^2}}$
- $\dfrac{1}{1+x^2}$
- $\dfrac{1}{\sqrt{1+x^2}}$
- $\dfrac{1}{\sqrt{1-x^2}}$
Show answer and solution
Correct answer: D. $\dfrac{1}{\sqrt{1-x^2}}$
If $y = \sin^{-1}x$, then $\sin y = x$, so $\cos y \cdot dy/dx = 1$, $dy/dx = 1/\cos y = 1/\sqrt{1 - x^2}$ (taking principal value).