Honors Geometry Companion Book, Volume 2

11.2.4 Circles in the Coordinate Plane - Worksheet

Example 1: Write the equation of each circle. 1.  A with center A (3, − 5) and radius 12

2.  B with center B ( − 4, 0) and radius 7

3.   M that passes through (2, 0) and that has center M (4, 0)

4.   N that passes through (2, − 2) and that has center N ( − 1, 2)

Example 2: Graph each equation. 5. ( x − 3) 2 + ( y − 3) 2 = 4

6. ( x − 1) 2 + ( y + 2) 2 = 9

7. ( x + 3) 2 + ( y + 4) 2 = 1

8. ( x − 3) 2 + ( y + 4) 2 = 16

Example 3: 9. A radio antenna tower is kept perpendicular to the ground by three wires of equal length. The wires touch the ground at three points on a circle whose center is at the base of the tower. The wires

touch the ground at A (2, 6), B ( − 2, − 2), and C ( − 5, 7). a. What are the coordinates of the base of the tower?

b. Each unit of the coordinate plane represents 1 ft. What is the diameter of the circle?

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