How to Show that PL is a Matrix in Vector Projection?

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SUMMARY

The discussion focuses on demonstrating that the projection operator PL is represented as a matrix in vector projection. The matrix representation of PL, given a direction vector d = [a, b, c], is defined as 1/(a² + b² + c²) multiplied by the matrix:

[a² ab ac; ab b² bc; ac bc c²]. It is clarified that PL is a linear transformation, and the matrix representation is straightforward when the basis aligns with the direction vector components. The participants express confusion regarding the notation used to represent the matrix.

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Let PL an QL denote, respectively, projection on and reflection in the line L through the origin with direction vector d = [a b c] =not 0

I got a proplem showing that PL is a matrix.

1/(a^2 +b^2+c^) = Matrix...a^2 ab ac
.........ab b^2 bc
.........ac bc c^2
 
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John Smith said:
Let PL an QL denote, respectively, projection on and reflection in the line L through the origin with direction vector d = [a b c] =not 0

I got a proplem showing that PL is a matrix.

1/(a^2 +b^2+c^) = Matrix...a^2 ab ac
.........ab b^2 bc
.........ac bc c^2
Strictly speaking, PL is a linear transformation. You are talking about it's matrix representation in the basis in which the given line has direction vector with components [a b c]. Now, unfortunately, I have no idea what you mean by "1/(a^2+ b^2+ c^2)= Matrix ...!

Given a vector [x y z], how would you find its projection, PL[x y z]? I get that the matrix representation is a very simple diagonal matrix.
 

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