How to Find an Explicit Description of a Plane from an Implicit Equation?

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Discussion Overview

The discussion centers on finding an explicit description of a plane from an implicit equation, specifically how to express a plane as the span of two vectors. The context involves mathematical reasoning related to vector spaces and plane equations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on how to derive an explicit description of a plane given its implicit equation, specifically asking about the equation 3x + 2y - z = 0.
  • Another participant questions what is meant by "explicit description" and asks for clarification on what specific information about the plane is being sought.
  • A clarification is provided that an explicit description refers to expressing the plane as the span of a two-vector set.
  • It is noted that describing the plane as a span is only valid if the plane passes through the origin; otherwise, a constant vector must be included.
  • A method is suggested for finding two vectors that span the plane by solving for one variable in terms of the others, leading to a parameterization of the plane.
  • A participant expresses appreciation for the clarification and confirms that the suggested approach aligns with their thinking.

Areas of Agreement / Disagreement

Participants generally agree on the method for finding a span of the plane, but there is a need for clarification on the definition of "explicit description." The discussion remains somewhat unresolved regarding the interpretation of the term.

Contextual Notes

The discussion does not resolve the assumptions regarding the definitions of explicit and implicit descriptions, nor does it clarify the conditions under which the span representation is valid.

hogrampage
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I understand how to find an implicit description if given the span of, say, two vectors. How do I go about finding an explicit description of a plane as the span of two vectors? For example, where would I start if the plane equation was:

3x+2y-z = 0

Thanks!
 
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What do you mean with "explicit description"? What is it of the plane that you would like to know?
 
i.e. Describe the plane as the span of a two-vector set.
 
hogrampage said:
i.e. Describe the plane as the span of a two-vector set.
You can only do that if the plane passes through the origin. Otherwise, it is such a span plus some constant vector.

But in your example, the plane passes through the origin, and the simplest way to find two vectors spanning the plane is to solve for one variable and put the others as parameters, say:
z=3x+2y, which leads to

##x=s##, ##y=t##, ##z=3s+2t##, or

##[x\,\, y\,\, z]^T=[s\,\, t\,\, 3s+2t]^T=s[1\, \,0\,\, 3]^T+t[0\,\,1\,\,2]^T##.
 
Okay, that is what I was thinking, but wasn't positive.

Thank you
 

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