# math

The image of the point (1, -2) after a rotation of 180° about the origin is

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asked by janine
1. (-1,+2) by inspection

using 90 deg matrix
R90 =
|+0 -1|
|+1 +0|
R180 is R90 * R90
|+0 -1||+0 -1|
|+1 +0||+1 +0|
which is
|-1 +0|
|+0 -1|

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posted by Damon
2. |-1 +0| |+1|
|+0 -1| |-2|

= (-1, +2 )

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posted by Damon

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