Chapter 10.6 Equations of Circles:
I) Standard equation of a circle with radius r and center (h,k) is:
r2 = (x - h)2 + (y - k)2
OR
r = √((x - h)2 + (y - k)2)
Example: Given circle O with center point (5, 3) and radius of 6, what is the standard equation of circle O?
r2 = (x - h)2 + (y - k)2
62 = (x - 5)2 + (y - 3)2
36 = (x - 5)2 + (y - 3)2
Example: Given circle O with center point ( -2, 4) and radius of 9, what is the standard equation of circle O?
92 = (x - -2)2 + (y - 4)2
81 = (x + 2)2 + (y - 4)2
Example: Given the standard equation of circle O: (x + 12)2 + (y - 4)2 = 25, what is the center point and radius?
center point is (-12, 4) and radius of 5
