1. Writing Equations of Circles

2. Remember Equation: (x-h) 2 +(y-k) 2 =r 2 Center (h, k) Radius = r So, to write the equation of a circle, we need the center point and the radius.

3. Write the equation of a circle given: It’s center is the point (-2, 5) and it passes through the point (1, 3)

4. Write the equation of a circle given:

5. The end points of it’s diameter are (-3, 11) and (3, -13)

6. Write the equation of a circle given:

7. It’s center is (-15, 9) and it is tangent to x=-17

8. Write the equation of a circle given: It’s center is (-15, 9) and it is tangent to x=-17 Using this visual we know that the radius of the circle is 2.

9. Write the equation of a circle given: It’s center lies on the x axis and it is tangent to x=7 and x=-13

10. Write the equation of a circle given: It’s center lies on the x axis and it is tangent to x=7 and x=-13 Using this visual we know that the diameter of the circle is 20, which makes the radius 10. Since the center is on the x-axis we know the y value is 0, and since it must be half way between the two tangent lines, it must be the point (-3, 0)

11. Assignment Writing Equations of Circles Worksheet