AlgebraLab

Algebra II Recipe: Graphing an Equation of a Circle

By G Redden

How to Graph a Circle
  1. Write the equation in standard form x2 + y2 = r2
  2. Determine the center and graph it.
    • If the center is not (0,0), remember it's the (h,k) of (x - h)2 + (y - k)2 = r2.
  3. Determine the radius. 
  4. Graph four points.
    • The distance from these four points to the center must be equal to the length of the radius.
  5. Connect the points with a circle.
1.
Graph y2 = 25 - x2
2.
Graph (x + 1)2 + (y - 5)2 = 49