Intersection of Two Planes in R3: Always a Line?

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SUMMARY

The statement "The intersection of two planes in R3 is always a line" is true, as two planes can either be parallel or intersect along a line. In R3, if two planes are not parallel, they will intersect in a line due to their infinite extent. To mathematically prove this, one can utilize the cross product of the normals of each plane, which provides a vector that is perpendicular to both normals, indicating the direction of the line of intersection.

PREREQUISITES
  • Understanding of R3 geometry and the concept of planes
  • Knowledge of vector operations, specifically the cross product
  • Familiarity with normal vectors of planes
  • Basic principles of linear algebra
NEXT STEPS
  • Study the properties of planes in three-dimensional space
  • Learn about the cross product and its applications in geometry
  • Explore the concept of normal vectors and their significance in defining planes
  • Investigate the conditions under which two planes are parallel or intersecting
USEFUL FOR

Students of geometry, mathematics enthusiasts, and educators looking to deepen their understanding of three-dimensional space and the relationships between planes.

mirandasatterley
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Homework Statement



True or False: The intersection of two planes in R3 is always a line.

The Attempt at a Solution



I'm pretty sure that this statement is true because two planes can only be parallel, or they must intersect in a line because the are infinite.

But I have no ideas on how to prove this mathematically. Any ideas?
 
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Are you familiar with the cross product? If so, consider the cross product of the normals to each plane.

By the way, what if the planes are parallel?
 
Last edited:

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