View Full Version : Quick derivative question
fffbone
Jan10-04, 08:07 PM
How do you find the derivative of y=x^y ?
master_coda
Jan10-04, 08:19 PM
\begin{align*}
y&=x^y \\
\ln y&=y\ln x \\
\frac{y^\prime}{y}&=y^\prime\ln x+\frac{y}{x} \\
y^\prime\left(\frac{1}{y}-\ln x\right)&=\frac{y}{x} \\
y^\prime&=\frac{y^2}{x-xy\ln x}
\end{align*}
fffbone
Jan10-04, 08:45 PM
Not quite the answer I was looking for, but thanks any how. I already know how the problem is solved.
master_coda
Jan10-04, 08:50 PM
You asked me how to find the derivative. I showed you a way to do it. What were you looking for?
fffbone
Jan11-04, 12:27 AM
I was looking for something more like this: x'=y^(1/y)*(1/y^2-ln(y)/y^2).
I solved it though, guess just got stuck for a minute.
master_coda
Jan11-04, 09:54 AM
Usually people want the derivative of y wrt x. Plus, you gave an equation for y in terms of x and y.
fffbone
Jan11-04, 10:47 AM
Since y does not equal f(x), y can not be expressed in terms of x. We would have to express x in terms of y.
Of course, it would be much better if the equation was x=y^x, then it can be expressed as y=x^(1/x).
vBulletin® v3.8.7, Copyright ©2000-2012, vBulletin Solutions, Inc.