AlgebraLab

Algebra II Recipe: Writing an Equation of a Circle Given Its Center and a Point on the Circle

By G Redden

Writing an equation
  1. Use  
  2. Substitute the values of the center in place of h and k.
  3. Substitute the values of the center of the circle in place of x and y.
  4. Simplify the expression to find r (the radius).
  5. Substitute the radius value into x2 + y2 = r2 when the center is (0,0).
  6. Substitute the radius and center (h, k) into (x - h)2 + (y - k)2 = r2 when the center is NOT (0,0).
1.
Write the equation of the circle with center (0,0) and (5,1) is a point on the circle.
2.
Write the equation of the circle with center (-2,3) and (3,3) is a point on the circle.