What do the blanks mean in this rotating vectors problem?

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g.lemaitre
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Homework Statement


This is an answer to a problem involving rotating vectors

Printed answer to problem 15: a 2 by 2 matrix with entries -1 in the top left, blank in the top right and bottom left, and entries 1/2 times the square root of 2 with minus, plus, plus and plus signs in the other positions.


I can't figure out what the blank spaces mean. Are there 0's there? Are there 1's? Help.
 
g.lemaitre said:

Homework Statement


This is an answer to a problem involving rotating vectors

Printed problem 15 showing a 2 by 2 matrix with entries -1 in the top left, 1/2 times the square root of 2 and negative 1/2 times the square root of 2 in the middle row, and 1/2 times the square root of 2 twice in the bottom row, with blank entries shown as empty space.


I can't figure out what the blank spaces mean. Are there 0's there? Are there 1's? Help.

clamtrox said:
They are zeroes.

And the reason you can't see them is they are the same tannish-brown color as the background. I can see them because I'm colorblind. :smile:
 
LCKurtz said:
And the reason you can't see them is they are the same tannish-brown color as the background. I can see them because I'm colorblind. :smile:

:)

You can easily figure this out: all rotation matrices have determinant of 1 (so they are what's called orthogonal matrices). In fact, you can see that this matrix has determinant of -1, so technically it's not a rotation but some combination of reflection and rotation.