d/dx(sin⁻¹ x) =
A1/(1+x²)
B1/√(1−x²)
C−1/√(1−x²)
Dcos⁻¹ x
Answer & Solution
Correct answer: B. 1/√(1−x²)
To find the derivative of $y = \sin^{-1} x$, we use implicit differentiation:
1. **Rewrite the function:** Let $y = \sin^{-1} x$. This is equivalent to saying $\sin y = x$.
2. **Differentiate both sides:** Apply the derivative with respect to $x$ to both sides of $\sin y = x$. Using the Chain Rule on the left side, we get:
$$\frac{d}{dx}(\sin y) = \frac{d}{dx}(x)$$
$$\cos y \cdot \frac{dy}{dx} = 1$$
3. **Solve for $\frac{dy}{dx}$:**
$$\frac{dy}{dx} = \frac{1}{\cos y}$$
4. **Convert back to $x$:** We know from the Pythagorean identity that $\sin^2 y + \cos^2 y = 1$. Therefore, $\cos y = \sqrt{1 - \sin^2 y}$. Since we defined $\sin y = x$, we substitute $x$ in:
$$\cos y = \sqrt{1 - x^2}$$
5. **Final Result:** Substitute this back into the expression for $\frac{dy}{dx}$:
$$\frac{d}{dx}(\sin^{-1} x) = \frac{1}{\sqrt{1 - x^2}}$$
Note: This is valid for $-1 < x < 1$.
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