RE: Derivative help
- To: mathgroup at smc.vnet.net
- Subject: [mg39154] RE: [mg39139] Derivative help
- From: "David Park" <djmp at earthlink.net>
- Date: Fri, 31 Jan 2003 19:57:02 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Steve, If you are new to Mathematica and expect to make a substantial use of it, then I strongly recommend working through Part I of The Mathematica Book. By actually typing in and trying the various Mathematica commands you will save a lot of time in the long run. Steven Wolfram's essay "Suggestions about Learning Mathematica" at the front of the book is very good advice. You can take the derivative of you function in the following ways. First, if you don't actually want to define the function you could write... D[Log[x]^n, x] (n*Log[x]^(-1 + n))/x Or you could define the function and then write the derivative... f[x_] := Log[x]^n f'[x] (n*Log[x]^(-1 + n))/x If you want to consider n to be a parameter and x to be the variable, then you could define your function this was... Clear[f] f[n_][x_] := Log[x]^n You could then take derivatives with respect to the variable using different parameters... f[q]'[y] (q*Log[y]^(-1 + q))/y or f[5]'[x] (5*Log[x]^4)/x And there are even more things to know about writing derivatives, but that should help you with your immediate question. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Steve Chiang [mailto:stevezx at attbi.com] To: mathgroup at smc.vnet.net Hi, all. I'm new to Mathematica. I went to the help section for my question but it only further confused me. I'm basically trying to take the first derivative of (ln(x))^x. Here is my syntax: f = (ln(x))^x. But then when I evaluate f ', it says nothing but ((ln(x))^x)' which is nothing new. Is this because I didn't specify bounds and that the function may be discontinuous over the default bounds in Mathematica? Thanks