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Solving implicit equation of a plane

  1. Oct 12, 2011 #1

    Can someone tell me if what I am doing is correct. I am trying to solve this equation of 0 = n ( p - p0 ) where n, p, and p0 are points on the plane. Assume this is a 2D dimension (x,y). Is this the correct way of calculating this equation.

    0 = nx (px - p0x) + ny (py + p0y)

    Purpose: I am trying to find if point p resides on the positive or negative side of the plane.

    Only help if you know the answer please.

  2. jcsd
  3. Oct 12, 2011 #2


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    You do have a typo (should be py - p0y).

    Your question is vague. What do you mean by positive or negative side of the plane? All your points are in the plane.
  4. Oct 12, 2011 #3
    You are right about the typo, my bad. Thanks.

    To clarify my question with an example, assume i have n and p0 given as n= (1,1) and p0=(2, 3). Now, say I have the following set of p {(1,3), (2,4), (1,5), (0,1), (2,3), (3,1)}. I would like to know where does each of the elements in the p set reside with respect to the plane. That is, it is on the positive side of the plane, zero, or negative? solving the equation should give me that answer.

    Is this the correct way to solve this equation:

    0 = nx (px - p0x) + ny (py - p0y)

  5. Oct 13, 2011 #4


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    I still don't know what you mean by positive side or negative side? If n, p0, and all the p's are given, the dot product you wrote has a definite value in each case. To = 0, p-p0 is perpendicular to n-(0,0).
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