For any triangle, and, in particular, any right triangle, there is exactly one circle containing all three vertices of the triangle. ("Sketch of proof". The locus of points equidistant from two given points is a straight line that is called the perpendicular bisector of the line segment connecting the points. The perpendicular bisectors of any two sides of a triangle intersect in exactly one point. This point must be equidistant from the vertices of the triangle.) This circle is called the circumcircle of the triangle.