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# help with rotation in geometry.?

figure TUV is graphed T (1,1) U (2, 5) V (4,0)

1. Find the coordinates of the vertices of triangle TUV after a 90 degree counter clockwise rotation.

2.Find the coordinates of the vertices of triangle TUV after a 90 degree clockwise rotation.

3.find the coordinates of the vertices of triangle TUV after a 180 degree clockwise rotation.

### 1 Answer

- MorewoodLv 71 decade agoFavorite Answer
You may need to clarify what level you are working at.

If I were asked to do that, I would write the points as column vectors and multiply by the rotation matrix:

/ cos(Angle) sin(Angle) \

\-sin(Angle) cos(Angle) /

Many calculators now do matrix multiplication, and I have computer programs I wrote for precisely these calculations. However, for the angles you request the matrix coefficients are all 0 or 1 or -1. Easy to multiply!

Another alternative is to take a piece of graph paper, draw the figure, rotate the paper, and read off the new coordinates after relabeling the new x-axis and the new y-axis.

Source(s): Matrix Multiplication: http://en.wikipedia.org/wiki/Matrix_multiplication or http://people.hofstra.edu/Stefan_Waner/realWorld/t...