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Homework Help: Vector calculus: Projection of a point to a plane

  1. Feb 8, 2006 #1
    The problem reads as follows:

    "The projection of a point P = (x,y,z) to a plane is a point on the plane that is closest to P. If the plane is defined by a point P0 = (x0,y0,z0) and a normal vector n=(x1,y1,z1), computer the projection of P on this plane."

    Well, I haven't had a relevant Calculus course in many years, but I'm 99.9% certain that this is a vector calculus problem. My memory is a little sketchy on how to solve for a projection of a point on to a plane, so could anyone here perhaps provide a forumla, algorithm, solution or some other explanation of this problem? Thank you all very much for your time and help even if you don't reply! :)
  2. jcsd
  3. Feb 8, 2006 #2


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    First find the projection Q of P-P0 onto n. If you think about it geometrically this is the vector connecting P and the closest point on the plane. Then if you take P - Q, you should be able to see that this is the projection of P onto the plane.
  4. Feb 8, 2006 #3
    its not a vector calculus problem its a 3D mathematics problem or a lin alg problem. You could do either orthodontist method which works good or you can try one of two other methods
    [0] you can find teh equation that passes between the point P and projP. Which is easy then substitue back into the plane equation and solve for t.
    lot mor work but its worth it
    [1] (this is just another way to reword orthodontist, but i think more in lamens terms)
    solve for the distance D of P to the plane. which is easy then add a "vector" with length with that distance
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