Tangent plane, why is it orthongonal and not parallel?

In summary: The plane is perpendicular to the vectors.In summary, the Homework statement is trying to find equation of the plane which is perpendicular to vector <-2,1,5>.
  • #1
flyingpig
2,579
1

Homework Statement




Find equation of the plane

The plane though P(6,3,2) and is perpendicular to vector <-2,1,5>

Why would it be -2(x - 6) + (y - 3) + 5(z - 2) = 0?

If it is perpendicular to <-2,1,5>, shouldn't be the cross product of some other vector with this? Using <-2,1,5> wouldn't mean it is parallel to the vector instead?



The Attempt at a Solution

 
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  • #2
Are you saying the CROSS product of two perpendicular vectors is zero? If not what are you saying?
 
  • #3
I am saying that

[PLAIN]http://img34.imageshack.us/img34/9647/unledseh.jpg

A plane's direction is determined by it's normal vector right? So if it is perpendicular to the vector <2,-1,5>, why would its normal vector be the same as <2,-1,5>?
 
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  • #4
flyingpig said:
I am saying that

[PLAIN]http://img34.imageshack.us/img34/9647/unledseh.jpg

A plane's direction is determined by it's normal vector right? So if it is perpendicular to the vector <2,-1,5>, why would its normal vector be the same as <2,-1,5>?

Perpendicular means the same thing as normal, as far as I know. If the plane is perpendicular to <2,-1,5> then it's also normal to <2,-1,5>. I'm really not sure what your question is. The normal vector is not parallel to the plane if that's what confusing you. Describing it as the 'direction of the plane' doesn't mean it's parallel to the plane.
 
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  • #5
But <2,-1,5> is just a scalar multiple of <2,-1,5> (scalar = 1), that is parallel?
 
  • #6
flyingpig said:
But <2,-1,5> is just a scalar multiple of <2,-1,5> (scalar = 1), that is parallel?

I may have figured out what is confusing you. A plane doesn't have a unique parallel direction. So the phrase 'direction of the plane' means its normal. Not its parallel. See my previous post.
 
  • #7
Is it because of this?

[PLAIN]http://img841.imageshack.us/img841/6863/unleditl.jpg
 
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  • #8
I have no clue what that is supposed to represent. However, I do note that you asked about a plane and a vector but your pictures show only two vectors, no plane.
 
  • #9
Oh, that is supposed to be a plane and the two vectors lie on the plane
 

FAQ: Tangent plane, why is it orthongonal and not parallel?

What is a tangent plane?

A tangent plane is a flat surface that touches a curved surface at a single point. It is used to approximate the behavior of a curved surface at that specific point.

Why is the tangent plane orthogonal?

The tangent plane is orthogonal, or perpendicular, to the normal vector of the curved surface at the point of contact. This is because the normal vector represents the direction of steepest ascent on the curved surface, and the tangent plane must be perpendicular to this direction in order to approximate the behavior of the surface accurately.

How is the tangent plane different from a parallel plane?

The tangent plane and a parallel plane are different in that the tangent plane touches the curved surface at a single point, while a parallel plane does not touch the curved surface at all. Additionally, the tangent plane is always perpendicular to the normal vector of the curved surface, whereas a parallel plane can be positioned at any angle.

Can the tangent plane ever be parallel to the curved surface?

No, the tangent plane can never be parallel to the curved surface. This is because the tangent plane is always perpendicular to the normal vector of the curved surface at the point of contact.

How is the tangent plane used in calculus?

In calculus, the tangent plane is used to approximate the behavior of a curved surface at a specific point. This is important in finding the slope of a curve, calculating derivatives, and solving optimization problems.

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