Linear Transformations

Aryth

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Feb 21, 2012
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Let \(\displaystyle R:\bold{R}^3 \rightarrow \bold{R}^3\) by perpendicular reflection across the plane \(\displaystyle x+2y-3z=0\)

i) Find two independent vectors in \(\displaystyle \bold{R}^3\) which map onto themselves.

ii) Find a vector in \(\displaystyle \bold{R}^3\) which map onto its opposite.

In the last 5 minutes of my last class we flew through an \(\displaystyle \bold{R}^2\) version of this problem, but I do not have a grasp on it at all. Maybe if someone can explain in more detail how to acquire these two, that would be great. I know (i) is searching for a basis, but I am unsure of the method I should use to get the solution.
 
A reflection across the plane will not change a vector if the vector lies in the plane. Any two vectors belonging to the plane which do not belong to the same span are linearly independent, though it is possible to find two orthogonal vectors with this property as well.

A vector will map to its opposite if it is orthogonal to that plane.
 
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