Math Problem Statement

Find the derivative of the function g(x) = x^cos(x).

Solution

The given function is:

g(x)=xcos(x)g(x) = x^{\cos(x)}

To find the derivative g(x)g'(x) of this function, we can use logarithmic differentiation, which is especially useful for functions where the exponent is also a function of xx.

Step-by-step solution:

  1. Take the natural logarithm of both sides: ln(g(x))=ln(xcos(x))\ln(g(x)) = \ln(x^{\cos(x)})

  2. Simplify using logarithm properties: ln(g(x))=cos(x)ln(x)\ln(g(x)) = \cos(x) \ln(x)

  3. Differentiate both sides with respect to xx: Use the chain rule on the left: g(x)g(x)=cos(x)1x+ln(x)(sin(x))\frac{g'(x)}{g(x)} = \cos(x) \cdot \frac{1}{x} + \ln(x) \cdot (-\sin(x))

    Simplifying this gives: g(x)g(x)=cos(x)xsin(x)ln(x)\frac{g'(x)}{g(x)} = \frac{\cos(x)}{x} - \sin(x) \ln(x)

  4. Solve for g(x)g'(x): Multiply both sides by g(x)=xcos(x)g(x) = x^{\cos(x)}: g(x)=xcos(x)(cos(x)xsin(x)ln(x))g'(x) = x^{\cos(x)} \left( \frac{\cos(x)}{x} - \sin(x) \ln(x) \right)

Final derivative:

g(x)=xcos(x)(cos(x)xsin(x)ln(x))g'(x) = x^{\cos(x)} \left( \frac{\cos(x)}{x} - \sin(x) \ln(x) \right)

Would you like more details or have any specific questions on this?

Here are 5 related questions to deepen understanding:

  1. How do you apply logarithmic differentiation in general?
  2. What is the domain of the function g(x)=xcos(x)g(x) = x^{\cos(x)}?
  3. How would you find the critical points of g(x)g(x)?
  4. Can g(x)g(x) have any asymptotes?
  5. How does g(x)g(x) behave as x0+x \to 0^+ and xx \to \infty?

Tip: Logarithmic differentiation is especially useful when dealing with expressions like f(x)g(x)f(x)^{g(x)}, where both the base and exponent are functions of xx.

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Math Problem Analysis

Mathematical Concepts

Calculus
Logarithmic Differentiation
Exponentiation

Formulas

g(x) = x^cos(x)
ln(g(x)) = cos(x) ln(x)
g'(x) = x^cos(x) (cos(x)/x - sin(x) ln(x))

Theorems

Logarithmic Differentiation

Suitable Grade Level

University level (Calculus)