SOLUTION: Rotate polygon ABCD 90 degree counterclockwise about the origin. A(-4,2) B(1,3) C(-2,1) D(-3,-2)

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Question 996837: Rotate polygon ABCD 90 degree counterclockwise about the origin.
A(-4,2)
B(1,3)
C(-2,1)
D(-3,-2)
Found 2 solutions by Edwin McCravy, Theo:
Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
Rules for rotating points about the origin

1. The point (a,b) rotated 90° counterclockwise about 
the origin becomes (-b,a).

2. The point (a,b) rotated 180° counterclockwise about 
the origin becomes (-a,-a).

3. The point (a,b) rotated 270° counterclockwise (or
90° clockwise) about the origin becomes (b,-a). 

We use rule 1:

A(-4,2) becomes A'(-2,-4)
B(1,3) becomes B'(-3,1)
C(-2,1) becomes C'(-1,-2)
D(-3,-2) becomes D'(2,-3)

The green polygon below rotated 90° counterclockwise 
about the origin becomes the red polygon:



Edwin
Answer by Theo(13342)   (Show Source): You can put this solution on YOUR website!
here's a reference on rotations.

http://www.regentsprep.org/regents/math/geometry/gt4/Rotate.htm

basically, a rotation of 90 degrees counterclockwise results in (x,y) becoming (-y,x).

(-4,2) becomes (-2,-4)
(1,3) becomes (-3,1)
(-2,1) becomes (-1,-2)
(-3,-2) becomes (2,-3)

if you look at each of those points individually, and extend a line from each point to the origin, you will see that they form a 90 degree angle.

here's what the original and the transformed point A looks like.

$$$








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