How can the length of a normal vector matter?

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Homework Help Overview

The discussion revolves around the role of the length of a normal vector in the context of tangent planes in multivariable calculus. Participants are exploring the implications of varying the scalar value associated with the normal vector in relation to the tangent plane's definition.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand intuitively how the length of a normal vector affects the tangent plane, questioning why it matters if the vector remains normal. Other participants discuss the necessity of both a normal vector and a point on the plane, and they raise questions about the effects of scaling the normal vector while maintaining its direction.

Discussion Status

The discussion is active, with participants providing insights into the relationship between the normal vector and the tangent plane. Some guidance has been offered regarding the need for both a normal vector and a point, and there is an exploration of the consequences of rescaling the normal vector.

Contextual Notes

Participants are considering the implications of the scalar value associated with the normal vector, specifically how it relates to the point through which the tangent plane passes. There is an underlying assumption that the normal vector must remain non-zero to maintain its role in defining the plane.

ainster31
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Homework Statement



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Homework Equations





The Attempt at a Solution



Solution:

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Graph:

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For part a, I understand mathematically why the value of c matters. What I don't understand is how it can possibly matter intuitively.

I get that ##\overrightarrow { \nabla } F(x_{ 0 },y_{ 0 },z_{ 0 })=(0,c,0)## and therefore, c can't be any value. My question is: how can a tangent plane possibly depend on the length of the normal vector? If the vector is normal, then the length shouldn't matter because the vector will always be normal for all values for c except 0.
 
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You need two pieces of information to specify the plane: the normal and a point on the plane. ##c## goes into figuring out what point the plane passes through.
 
vela said:
You need two pieces of information to specify the plane: the normal and a point on the plane. ##c## goes into figuring out what point the plane passes through.

What are the effects on a tangent plane when you scale up and down ∇F but keep ∇F in the same direction?
 
##\nabla F## is determined by F, so you don't have the freedom to arbitrarily rescale it. If you mean what happens if you say, for example, ##\nabla F = (0, c/2, 0)## instead of ##\nabla F = (0, c, 0)##, why don't you try it and see what happens?
 

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