Khan Academy

Terms & labels in geometry (K-A)

Euclid as the father of geometry (K-A)

Geometric definitions example (K-A)

Lines, line segments, & rays (K-A)

Specifying planes in three dimensions (K-A)

Terms & labels in geometry (K-A)

Angles in a triangle sum to 180° proof-video (K-A)

Intro to quadrilateral (K-A)

Kites as a geometric shape (K-A)

Proof: Opposite angles of a parallelogram- video (K-A)

Proof: Opposite sides of a parallelogram-video (K-A)

Quadrilateral properties (K-A)

Quadrilateral types (K-A)

Sum of interior angles of a polygon (K-A)

Sum of the exterior angles of a polygon (K-A)

Triangle angle challenge problem 2 (K-A)

Triangle angles review (K-A)

Triangle exterior angle example (K-A)

Triangle inequality theorem (K-A)

Worked example: Triangle angles (diagram) (K-A)

Worked example: Triangle angles (intersecting lines) (K-A)

Acute, right, & obtuse angles (K-A)

Angles, parallel lines, & transversals (K-A)

Area of a circle (K-A)

Complementary & supplementary angles (K-A)