Solving derivative of $x^x$ without logarithmic differentiation [duplicate]
With logarithmic differentiation, it is quite simple to compute the derivative of $x^x$:
$$y=x^x$$ $$\ln {y} =x \ln{x}$$ $$\frac {1}{y} \frac {dy}{dx} = \ln{x} +1$$ $$\frac {dy}{dx} =\left( ln(x)+1 \right) x^x.$$
Is there a method to compute the derivative of ${ x }^{ x }$ that does not rely on logarithmic differentiation?
Thanks to Brian M. Scott for the comment that led to this solution:
$y={ x }^{ x }={ e }^{ x\ln { x } }\\ \frac { dy }{ dx } =\left( \ln(x)+1 \right) { e }^{ x\ln { x } }\\ \frac { dy }{ dx } =\left( \ln(x)+1 \right) { x }^{ x }\\ $
There's another way that looks like a gross blunder but actually is perfectly correct. I will illustrate it on the more general question, differentiate $y=f(x)^{g(x)}$.
If $g$ were constant, we'd get $f'(x)g(x)f(x)^{g(x)-1}$.
If $f$ were constant, we'd get $g'(x)f(x)^{g(x)}\log f(x)$.
Add these together to get the answer: $$y'=f'(x)g(x)f(x)^{g(x)-1}+g'(x)f(x)^{g(x)}\log f(x)$$
It's easy to see that in the original problem, where $f(x)=x$ and $g(x)=x$, this reduces to $x^x+x^x\log x$, as obtained by other methods.