From help-request at octave dot org Sun Mar 20 09:59:12 2005 Subject: Re: plotting even function From: "John B. Thoo" To: sct at ucsd dot edu Cc: help at octave dot org Date: Sun, 20 Mar 2005 08:07:04 -0800 Hi, Steve. I'm sorry for dragging this out, but I'm not yet understanding. Why is x^(2/3) equal to (x^(1/3))^2 but x^(2/3) not equal to (x^2)^(1/3)? Also, why is (x^(1/3))^2 not even? If f(x) = (x^(1/3))^2, then isn't f(-x) = ((-x)^(1/3))^2 = (- x^(1/3))^2 = (x^(1/3))^2 = f(x) (for real x)? I must not be understanding something rudimentary. TIA. ---John. (a numerical computation and Octave novice) On Mar 19, 2005, at 5:03 PM, Steve C. Thompson wrote: > John, > > Could this be it? > > x^(2/3) is equal to (x^(1/3))^2 which isn't even. > > x^(2/3) is not equal to (x^2)^(1/3) which is even. > > > Steve > > > On Mar 19 16:20PM, John B. Thoo wrote: >> Hi. I hope that I'm not embarrassing myself by asking the following. >> >> I believe that >> >> 3 2/3 1 >> y = --- (2 x) + --- >> 4 2 >> >> is an even function, yet >> >> x = -1:0.04:1; >> plot (x, 0.75 * (2 .* x).^(2 / 3) + 0.5) >> >> is not symmetrical about the y-axis. What is wrong with my thinking? >> >> TIA. >> ---John. >> >> >> >> ------------------------------------------------------------- >> Octave is freely available under the terms of the GNU GPL. >> >> Octave's home on the web: http://www.octave.org >> How to fund new projects: http://www.octave.org/funding.html >> Subscription information: http://www.octave.org/archive.html >> ------------------------------------------------------------- >> > ------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html -------------------------------------------------------------