Logarithmic Derivative
1. **Problem:** Find the derivative of the function $$f(x) = x^{4 - x^2}$$ using logarithmic differentiation.
2. **Step 1: Apply logarithm to both sides**
Take the natural logarithm: $$\ln f(x) = \ln \left(x^{4 - x^2}\right)$$
Using log rules: $$\ln f(x) = (4 - x^2) \ln x$$
3. **Step 2: Differentiate both sides implicitly with respect to $$x$$**
Recall $$\frac{d}{dx} \ln f(x) = \frac{f'(x)}{f(x)}$$ and use product rule on right side:
$$\frac{f'(x)}{f(x)} = \frac{d}{dx} \left((4 - x^2) \ln x \right) = (4 - x^2) \frac{1}{x} + \ln x \frac{d}{dx} (4 - x^2)$$
4. **Step 3: Compute the derivative of inside terms**
$$\frac{d}{dx} (4 - x^2) = -2x$$ therefore:
$$\frac{f'(x)}{f(x)} = \frac{4 - x^2}{x} + \ln x (-2x)$$
5. **Step 4: Multiply both sides by $$f(x)$$ to solve for $$f'(x)$$**
Recall $$f(x) = x^{4 - x^2}$$, so:
$$f'(x) = x^{4 - x^2} \left( \frac{4 - x^2}{x} - 2x \ln x \right)$$
6. **Final answer:**
$$f'(x) = x^{4 - x^2} \left( \frac{4 - x^2}{x} - 2x \ln x \right)$$
This expresses the derivative clearly using logarithmic differentiation and product rule, showing all intermediate steps and explanations.