Find f′(x)f^{\prime}(x) if f′(x)=(sin⁡x)sin⁡xf^{\prime}(x)=(\sin x)^{\sin x} for all 0<x<π0<x<\pi.

Answer: f′(x)=(sin⁡x)sin⁡xcos⁡x[ln⁡(sin⁡x)+1]f^{\prime}(x) = (\sin x)^{\sin x} \cos x [\ln (\sin x) + 1]

Step-by-step solution

Step 1: Take the natural logarithm of both sides

To differentiate a function of the form u(x)v(x)u(x)^{v(x)}, it is often helpful to use logarithmic differentiation. We start by taking the natural logarithm of both sides of the equation.

Step 2: Apply logarithm property

Using the logarithm property ln⁡(ab)=bln⁡a\ln(a^b) = b \ln a, we can simplify the right-hand side of the equation.

Step 3: Differentiate both sides with respect to x

Now, we differentiate both sides of the equation with respect to xx. On the left side, we use the chain rule. On the right side, we will use the product rule.

Step 4: Apply product rule and chain rule

Applying the product rule ddx(uv)=u′v+uv′\frac{d}{dx}(uv) = u'v + uv' to the right side, where u=sin⁡xu = \sin x and v=ln⁡(sin⁡x)v = \ln(\sin x). The derivative of sin⁡x\sin x is cos⁡x\cos x, and the derivative of ln⁡(sin⁡x)\ln(\sin x) is 1sin⁡x⋅cos⁡x\frac{1}{\sin x} \cdot \cos x by the chain rule.

Step 5: Simplify the expression

We simplify the right-hand side by canceling out sin⁡x\sin x in the second term.

Step 6: Solve for f′(x)f^{\prime}(x)

Finally, we multiply both sides by f(x)f(x) and substitute back f(x)=(sin⁡x)sin⁡xf(x) = (\sin x)^{\sin x}. We can also factor out cos⁡x\cos x from the expression.

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