The problem asks us to use implicit differentiation to find $y'$, given the equation $x^y = y^x$.

CalculusImplicit DifferentiationDerivativesLogarithms
2025/5/15

1. Problem Description

The problem asks us to use implicit differentiation to find yy', given the equation xy=yxx^y = y^x.

2. Solution Steps

We are given xy=yxx^y = y^x. Taking the natural logarithm of both sides, we get
ln(xy)=ln(yx) \ln(x^y) = \ln(y^x)
Using the logarithm property ln(ab)=bln(a)\ln(a^b) = b \ln(a), we have
yln(x)=xln(y) y \ln(x) = x \ln(y)
Now we differentiate both sides with respect to xx using the product rule.
ddx(yln(x))=ddx(xln(y)) \frac{d}{dx}(y \ln(x)) = \frac{d}{dx}(x \ln(y))
dydxln(x)+y1x=1ln(y)+x1ydydx \frac{dy}{dx} \ln(x) + y \frac{1}{x} = 1 \cdot \ln(y) + x \frac{1}{y} \frac{dy}{dx}
yln(x)+yx=ln(y)+xyy y' \ln(x) + \frac{y}{x} = \ln(y) + \frac{x}{y} y'
Now we want to isolate yy'.
yln(x)xyy=ln(y)yx y' \ln(x) - \frac{x}{y} y' = \ln(y) - \frac{y}{x}
y(ln(x)xy)=ln(y)yx y' \left( \ln(x) - \frac{x}{y} \right) = \ln(y) - \frac{y}{x}
y=ln(y)yxln(x)xy y' = \frac{\ln(y) - \frac{y}{x}}{\ln(x) - \frac{x}{y}}
Multiply both the numerator and the denominator by xyxy:
y=xyln(y)y2xyln(x)x2 y' = \frac{xy \ln(y) - y^2}{xy \ln(x) - x^2}

3. Final Answer

y=xyln(y)y2xyln(x)x2 y' = \frac{xy \ln(y) - y^2}{xy \ln(x) - x^2}