Re: Plot results not right

*To*: mathgroup at smc.vnet.net*Subject*: [mg90008] Re: Plot results not right*From*: Narasimham <mathma18 at hotmail.com>*Date*: Thu, 26 Jun 2008 04:43:04 -0400 (EDT)*References*: <g3nhbc$g6$1@smc.vnet.net>

On Jun 23, 11:54 am, BrenB <GoogleGro... at ebesser.com> wrote: > Plot[2 x - 3 x^(2/3) + 4, {x, -1, 6}] > > The output graph is correct, except there should be graphing in the > 2nd and 3rd quadrant, and there is none. By cubing & simplifying or by Expand we can handle the troublesome region x< 0. Expand[(y - 4 - 2 x)^3 ] + 27 x^2 ContourPlot[% == 0, {x, -1, 6}, {y, -1, 6}, GridLines -> Automatic] or ContourPlot[-64 - 96 x - 21 x^2 - 8 x^3 + 48 y + 48 x y + 12 x^2 y - 12 y^2 - 6 x y^2 + y^3 == 0, {x, -1, 6}, {y, -1, 6}, GridLines -> Automatic] which gets the plot. At the cusp point (x,y) = (0,4) the curve slope is indeterminate and curvature infinite.