Posted by **janine** on Monday, July 18, 2011 at 5:17pm.

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

- math -
**Damon**, Monday, July 18, 2011 at 5:35pm
(-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|

- continued -
**Damon**, Monday, July 18, 2011 at 5:36pm
|-1 +0| |+1|

|+0 -1| |-2|

= (-1, +2 )

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