Linear Algebra: Parallel, Perpendicular, or Neither?

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Homework Help Overview

The problem involves determining the relationship between a line defined by a point and a direction vector and a plane given by a linear equation in three-dimensional space. The subject area is linear algebra, focusing on concepts of parallelism and perpendicularity in vector spaces.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss relating the line's direction vector to the plane's normal vector, questioning how these vectors interact. There is exploration of the implications of scalar multiples and the use of cross and dot products to establish relationships.

Discussion Status

The discussion has progressed with participants suggesting that the normal vector of the plane is parallel to the line, and some express the belief that this implies perpendicularity between the line and the plane. However, the mathematical proof of this relationship remains a point of inquiry.

Contextual Notes

Participants are navigating the definitions and relationships between vectors in the context of linear algebra, with an emphasis on understanding the implications of vector relationships without reaching a definitive conclusion.

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Homework Statement



The line l passes through the point P=(1,-1,1) and has direction vector d=[2,3,-1]. Determine whether l and P are parallel, perpendicular, or neither to 2x+3y-z=1.

Homework Equations


n.p=n.x, cross product, dot product


The Attempt at a Solution


Would you just relate the direction vector, d, to the normal vector, n[2,3,-1] ?
 
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Yes, you would just relate the normal vector to the direction vector. How do they relate?
 
they would be parallel because they are scalar multiples of one another (1 is the multiple) also the cross product would be zero indicating parallel vectors.
 
That means that the NORMAL to the plane is parallel to the line. So what's the relation between the line and the plane?
 
that they are perpendicular?
 
Yes, they are.
 
How would you prove that mathematically?
 
What's to prove? The normal vector of the plane is parallel to the line. You proved that by showing they are scalar multiples or using the cross product. You're done.
 

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