One of the five given matrices represents an orthogonal projection onto a line and another represents a reflection about line. Identify both and briefly justify your choice.02510501111.png

Khadija Wells

Khadija Wells

Answered question

2021-03-26

One of the five given matrices represents an orthogonal projection onto a line and another represents a reflection about line. Identify both and briefly justify your choice.
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Answer & Explanation

delilnaT

delilnaT

Skilled2021-03-28Added 94 answers

Consider L be a line in R3
Orthogonal projection of x onto the line L is,
projL(x)=(xu)u
Here u is a unit vector parallel to the line L.
Let
u=(u1u2u3)
Now projL(x)=(xu1+yu2+zu3)(u1u2u3)
Consider the matrix B=13(111111121)
Consider the corresponding linear transformation that representled by the matrix B.
Bx=13(111111111)x
=13(111111111)(xyz)
=13(x+y+zx+y+zx+y+z)
=(13x+13y+13z)(131313)
This linear transformation is of the form (1)
From (1), unit vector is,
u=(131313)
The line L is,
x=y=z
Hence, the matrix B represents an orthogonal projection onto the line L:x=y=z
Reflection of x onto the line L is,
refL(x)=2projL(x)x
=2(xu)ux
Now
refL(x)=2(xu)ux
=2(xu1+yu2+zu3)(u1u2u3)(xyz)
Consider the matrix

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