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Re: easy plane normal vector question

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  • Subject: [mg89738] Re: easy plane normal vector question
  • From: dh <dh at>
  • Date: Thu, 19 Jun 2008 05:44:33 -0400 (EDT)
  • References: <g3agp3$pjo$>

Hi Will,

write your equation in the form:




you see that the scalar product of {a,b} with any vector on (from origin 

to a point on the surface) the surface is -c. Therefore, as a vector in 

(between two points on) the surface is the difference between two 

vectors on the surface, the scalar product of a vector in the surface 

with {a,b} is zero. {a,b} is perpendicular to the surface.

hope this helps, Daniel

will parr wrote:

> Dear Math Forum,


> sorry but i'm not very good at vector maths, so this is probably a very easy question:


> if i have the equation for a plane in the form:


> plane = c + ax + by


> (for example plane=4.07919+ 0.0764884 x - 0.0632675 y)


> as you get if you use the Fit function to fit some 3D data (data) in the following way:


> Fit[data,{1, x, y},{x, y}],


> How do i calculate the normal vector to this plane?


> best wishes,


> Will



Daniel Huber

Metrohm Ltd.

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CH-9100 Herisau

Tel. +41 71 353 8585, Fax +41 71 353 8907

E-Mail:<mailto:dh at>


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