Chapter 9, Problem 20SGR

To determine

To perform the specified rotation of given figure.

Explanation of Solution

Given:

The vertices of triangle are $D(1,2),G(2,3)$ and $F(1,3)$ rotation of ${90}^{\circ }$

Calculation:

To rotate a point ${90}^{\circ }$ counter clockwise about the origin, multiply the y-coordinate by $-1$ and then interchange the x-coordinate and y-coordinate.

  $\begin{array}{l}(x,y)=(-y,x)\\ D(1,2)\to D\text{'}(-2,1)\\ G(2,3)\to G\text{'}(-3,2)\\ F(1,3)\to F\text{'}(-3,1)\end{array}$