Minimizing Volume in 3-Space: Plane Equation?

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Discussion Overview

The discussion revolves around finding the equation of a plane that passes through the point (1,1,1) and encloses the least amount of volume in the first octant. Participants explore different interpretations of the problem, particularly regarding the concept of volume and the conditions under which a plane can be said to enclose space.

Discussion Character

  • Debate/contested
  • Homework-related
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the equation of the plane could be y=x in 3-space, but questions the implications of the plane being on edge from (1,1,1) to the origin.
  • Another participant agrees with the teacher's assertion that there are infinitely many planes through (0,0,0) and (1,1,1) that do not enclose a bounded region in the first octant.
  • A participant questions the notion of cutting off zero volume, suggesting that it could be a valid interpretation depending on the problem's wording.
  • One participant proposes that it may be beneficial to solve the problem from both perspectives: finding a plane that minimizes volume while intersecting all three axes versus the initial interpretation.

Areas of Agreement / Disagreement

Participants express differing views on whether a plane can be said to enclose zero volume and the implications of the problem's wording. There is no consensus on the correct interpretation or solution to the problem.

Contextual Notes

The discussion highlights the ambiguity in the definition of 'enclose' and the conditions under which a plane can be said to cut off volume in the first octant. Participants acknowledge the need for clarity in the problem's wording.

cragar
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I once had a home work question that asked us to find the equation of a plane that went through the point (1,1,1) an enclosed the least amount of volume in the first octant . I know how to do it with derivatives and all that but what if the plane was on edge going from (1,1,1) to the origin . It would be like having a sheet of glass bisect the corner of the room but my teacher said that it had no top on it and it enclosed no volume , so what do you guys think ?
I think the equation of my plane would be y=x in 3-space .
 
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I think your teacher is completely correct! There are, in fact, an infinite number of planes passing through both (0, 0, 0) and (1, 1, 1) (y= x is one of them but rotating that around the line x= t+ 1, y= t+ 1, z= t+ 1 gives another for every angle of rotation between 0 and [itex]2\pi[/itex]) but none of then "cut off" a bounded region of the first octant.
 
why can't we say it cuts off zero volume .
 
Depending on the detailed wording of the problem (and the chosen definition of the word 'enclose'), you probably could.

But the best would be to solve the problem both ways, i.e. also assume that you're supposed to find the plane that cuts off the minimal volume in that octant, while intersecting somewhere on all three axes.

Then you'd have your "clever solution" as well as what is probably the "intended solution".
 
ya i was thinking it would work
 

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