
Euclid as the father of geometry  Introduction to Euclidean geometry  Geometry  Khan Academy

Basic geometry: language and labels  Introduction to Euclidean geometry  Geometry  Khan Academy

Area of a Regular Hexagon

Problem involving angle derived from square and circle

Area of a Parallelogram

Proof: Rhombus area half product of diagonal length  Quadrilaterals  Geometry  Khan Academy

Proof  Rhombus Diagonals are Perpendicular Bisectors

Proof  Opposite Angles of Parallelogram Congruent

Proof  Diagonals of a Parallelogram Bisect Each Other

Proof  Opposite Sides of Parallelogram Congruent

Quadrilateral Overview

Common Orthocenter and Centroid

Euler's Line Proof

Euler line  Special properties and parts of triangles  Geometry  Khan Academy

Review of Triangle Properties

Proof  Triangle Altitudes are Concurrent (Orthocenter)

Median Centroid Right Triangle Example