Re: Perpendicular lines do not appear perpendicular

*To*: mathgroup at smc.vnet.net*Subject*: [mg100337] Re: Perpendicular lines do not appear perpendicular*From*: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>*Date*: Mon, 1 Jun 2009 07:09:22 -0400 (EDT)*References*: <gvtmhv$gh8$1@smc.vnet.net>

Hi Bill, It looks perfectly perpendicular on my screen. Could you check the resolution to which your monitor is set? It might be that you have set it to a non native resolution with an aspect-ratio that's not 16:10 (which would be natural for your screen). Cheers -- Sjoerd On May 31, 12:35 pm, Bill <WDWNORW... at aol.com> wrote: > Perpendicular lines do not appear perpendicular > > Hi: > > I have taken the line equation 2*x+4*y-6==0, and rotated it 90 degree= s counterclockwise about {0,0}, > using a 3x3 rotation matrix. > Here's the Mathematica 6.0.1 code that I used: > > rMat = {{Cos[90 Degree], - Sin[90 Degree], 0}, {Sin[90 Degree], > Cos[90 Degree], 0}, {0, 0, 1}} > > l={2, 4, -6} > > rMat.l > > Output: {-4,2,-6} > > Placing these numbers into the general form of the equation of the line A= x+By+c=0, I get -4*x + 2*y - 6 == 0. > Placing the 2 perpendicular line equations into ContourPlot: > > ContourPlot[{2*x + 4*y - 6 == 0, -4*x + 2*y - 6 == 0}, {x, -4, > 4}, {y, -4, 4}, AspectRatio -> 1] > > and plotting, I notice that on my pc screen that the lines do not look pe= rpendicular, as does the plot frame. > Perhaps this is just my computer screen, a HP f2105. I can hold up a squa= re cut piece of paper to the lines > on the screen, and notice the out-of-square condition. I used AspectRatio= ->1, but still no joy. > > Question: Can someone suggest a remedy for my problem, if one exists? > > Thanks in advance, > > Bill > > PS. Mathematica 6.0.1 on a pc with Win XP.