How to Find the Normal Vector for a Plane Perpendicular to Another?

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SUMMARY

The discussion focuses on finding the scalar equation of a plane that is perpendicular to another plane defined by the normal vector [3,1,2] and passes through points A(2,-6,-1) and B(1,2,-4). To determine the normal vector of the new plane, participants highlight the need for the cross product of two vectors: the normal vector [3,1,2] and the direction vector from A to B, which is calculated as [-1, -4, -3]. The cross product will yield a vector that is perpendicular to both, thus serving as the normal vector for the new plane.

PREREQUISITES
  • Understanding of vector operations, specifically cross products.
  • Familiarity with scalar equations of planes in three-dimensional space.
  • Knowledge of vector representation and direction vectors.
  • Basic skills in coordinate geometry.
NEXT STEPS
  • Study the properties and applications of the cross product in vector mathematics.
  • Learn how to derive the scalar equation of a plane from a normal vector and a point on the plane.
  • Explore examples of finding normal vectors for various geometric configurations.
  • Investigate the implications of perpendicular planes in three-dimensional geometry.
USEFUL FOR

Mathematicians, physics students, and anyone involved in 3D modeling or computational geometry who needs to understand the relationships between planes and vectors.

eme_girl
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Find the scalar eq'n of a plane that is perpendicular to the plane with normal vector [3,1,2] and passes through points A(2,-6,-1) and B(1,2,-4).

I think that the normal vector can be the direction vector of this new plane. But then, in order to find the scalar eq'n I need a normal vector of this new plane. How do I find this?
 
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Strictly speaking a plane doesn't have a "direction vector". What is true is that the vector [3,1,2] is in the plane you want. You also know that the vector from A(2,6,-1) to B(1,2,-4) (which is, of course, [1-2,2-6,-4-(-1)]= [-1, -4, -3] is in the plane. Do you know how to find a vector that is perpendicular to both [3,1,2] and [1,4,-3]?
 
I understand what you just found. But no, I do not know how to find a vector's that perpendicular to both those vectors.
 
eme_girl,
do u know the direction of a vector that is a cross product of two vectors?

-- AI
 
TenaliRaman's point: the cross product of two vectors is always perpendicular to both.

The cross product of [a1,a2,a3] and [b1,b2,b3] is the vector [a2b3-a3b2,a3b1-a1b3,a1b2-a2b1].
 

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