Unfortunately I lost the article. Someone horrorflickchick... asked about an equation for a circle with given vertices.
The perpendicular bisectors of the sides of a triangle intersect at the same point which is equidistant from the vertices of the triangle.
Find the perpendicular lines which intersect the midpoints of any two of the sides; the lines so found intersect at a common point which is the center of the circle. Use distance formula to find the vertex to center of circle distance. Apply the appropriate values in a general or standard form equation of a circle.