Khan Academy: Geometry: Language and Notation of the Circle

Explains terms and notation of basic elements of geometry. [12:57]

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....

This video tutorial demonstrates solutions to problems #51-55 of the California Geometry released state test questions. Problems address proving and using the Pythagorean theorem and compass constructions. [12:35]

Demonstrates solutions to problems #56-60 of the California Geometry released state test questions. Problems address compass constructions, slope of perpendicular lines, and using the distance formula. [12:49]

Proof that the sum of the angles in a triangle is 180 using the relationship of angles formed when parallel lines are cut by a transversal. This video also appears in the Geometry: Triangles strand. [6:31]

Demonstrates solutions to problems #71-75 of California Geometry released state test questions. Problems address Pythagorean theorem, 45-45-90 triangles, 30-60-90 triangles, circumscribed polygons, area, chord length, tangents to circles...

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...

Worked example that uses the unit circle definition to evaluate trig functions. [11:24]

This video tutorial [5:35] explains that if the diameter of a circle is one of the sides of a triangle inscribed in the circle then the triangle is a right triangle. This video also appears in the strand Geometry: Circles.

Demonstrates solutions to problems #76-80 of California Geometry released state test questions. Problems address tangents to circles, secants to circles, intercepted arcs, translations on the coordinate plane, and rotations on the...