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Show that four points lie on a plane

  • Thread starter toupee
  • Start date
  • #1
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Homework Statement


(2; 0; 1); (-1; 2; 3); (3; 2; 2) and (3;-6;-3)

Homework Equations



PS→⋅(PR→×PQ→)=0

The Attempt at a Solution



Hi all, I am just wondering if my calculations are correct, and in fact these points do not lie on a plane. My answer is = 50 and i am not confident. Can anyone help me please?
 
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Answers and Replies

  • #2
Orodruin
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It would be much easier to judge if what you are doing is correct if you actually showed us what you are doing.

Edit: Also, the points do lie in a plane - any solution not resulting in this is going to be wrong.
 
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  • #3
ehild
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Hi all, I am just wondering if my calculations are correct, and in fact these points do not lie on a plane. My answer is = 50 and i am not confident. Can anyone help me please?
What is 50?

ehild
 
  • #4
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I have miss-read the question. All it is asking me to do, is prove that these points lie in the same plane. May i ask how?
 
  • #5
Orodruin
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If this is a homework problem or problem in a course you are taking there should be a description of how to determine this in your course literature. Have you tried applying that?
 
  • #6
HallsofIvy
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I have miss-read the question. All it is asking me to do, is prove that these points lie in the same plane. May i ask how?
You have the answer in your first post:
PS→⋅(PR→×PQ→)=0
(I assume the arrow after indicates "vector")

Any three points, such as P, Q, and R must lie in a plane so the two vectors PR and PQ lie in a plane and their cross product is perpendicular to the plane. The fourth point, S, lies in that same plane if and only the vector PS does also- and then its dot product with the perpendicular vector is 0.
 

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