Khan Academy
Khan Academy: Geometry: Three Points Defining a Circle
Demonstates that any three non-collinear points can be used to define a unique triangle with a unique circumcenter and circumradius. These, in turn, define a unique circle. The center of the circle is the circumcenter of the triangle....
Khan Academy
Khan Academy: Algebra: Conic Sections: Three Points Defining a Circle
A video lesson that describes how any three non-collinear points actually define a circle. First it is shown that three points define a triangle. Then it is shown that the circumcenter of that triangle is actually the center of the...
Khan Academy
Khan Academy: Geometry: Circumcenter of a Triangle
Explains using multiple proofs that a point on a perpendicular bisector is equidistant from the endpoints of the segment it bisects. Proofs use triangle congruency postulates. Lays the foundation for understanding the circumcenter of a...
Khan Academy
Khan Academy: Perpendicular Bisectors: Area Circumradius Formula Proof
Proof of the formula relating the area of a triangle to its circumradius.