Question #N140
A circle in the xy-plane has center (1,-2) and radius 5. Which of the following is an equation of this circle?
A. (x - 1)^2 + (y + 2)^2 = 5
B. (x + 1)^2 + (y - 2)^2 = 25
C. (x - 1)^2 + (y + 2)^2 = 25
D. (x + 1)^2 + (y - 2)^2 = 5
Correct Answer is: C
The standard form of the equation of a circle with center (h,k) and radius r is (x - h)^2 + (y - k)^2 = r^2. In this case, the center of the circle is (1,-2) and the radius is 5. Substituting these values into the standard form of the equation gives (x - 1)^2 + (y - (-2))^2 = 5^2, which simplifies to (x - 1)^2 + (y + 2)^2 = 25.