- 1 - Euclid as the Father of Geometry
- 2 - Language and Notation of Basic Geometry
- 3 - Lines, Line Segments, and Rays
- 4 - Language and Notation of the Circle
- 5 - Angle Basics
- 6 - Measuring Angles in Degrees
- 7 - Using a Protractor
- 8 - Measuring Angles
- 9 - Complementary and Supplementary Angles
- 10 - Angles at the intersection of two lines
- 11 - Proof-Vertical Angles are Equal
- 12 - Angles Formed by Parallel Lines and Transversals
- 13 - Proof - Sum of Measures of Angles in a Triangle are 180
- 14 - Triangle Angle Example 1
- 15 - Triangle Angle Example 2
- 16 - Triangle Angle Example 3
- 17 - Challenging Triangle Angle Problem
- 18 - Proof - Corresponding Angle Equivalence Implies Parallel Lines
- 19 - Finding more angles
- 20 - Sum of Interior Angles of a Polygon
- 21 - Congruent Triangles and SSS
- 22 - SSS to Show a Radius is Perpendicular to a Chord that it Bisects
- 23 - Other Triangle Congruence Postulates
- 24 - Two column proof showing segments are perpendicular
- 25 - Sum of the exterior angles of convex polygon
- 26 - Finding Congruent Triangles
- 27 - More on why SSA is not a postulate
- 28 - Congruent Triangle Proof Example
- 29 - Congruent Triangle Example 2
- 30 - Congruent legs and base angles of Isosceles Triangles
- 31 - Equilateral Triangle Sides and Angles Congruent
- 32 - Equilateral and Isosceles Example Problems
- 33 - Another Isosceles Example Problem
- 34 - Example involving an isosceles triangle and parallel lines
- 35 - Figuring out all the angles for congruent triangles example
- 36 - Perimeter and Area Basics
- 37 - Triangle Area Proofs
- 38 - Interesting Perimeter and Area Problems
- 39 - Koch Snowflake Fractal
- 40 - Area of an Equilateral Triangle
- 41 - Area of Koch Snowflake (part 1) - Advanced
- 42 - Area of Koch Snowflake (part 2) - Advanced
- 43 - Challenging Perimeter Problem
- 44 - Similar Triangle Basics
- 45 - Similarity Postulates
- 46 - Similar Triangle Example Problems
- 47 - Similarity Example Problems
- 48 - Challenging Similarity Problem
- 49 - Similarity example where same side plays different roles
- 50 - Finding Area Using Similarity and Congruence
- 51 - Pythagorean Theorem Proof Using Similarity
- 52 - 30-60-90 Triangle Side Ratios Proof
- 53 - 45-45-90 Triangle Side Ratios
- 54 - 30-60-90 Triangle Example Problem
- 55 - The Golden Ratio
- 56 - Introduction to angles (old)
- 57 - Angles (part 2)
- 58 - Angles (part 3)
- 59 - Angles formed between transversals and parallel lines
- 60 - Angles of parallel lines 2
- 61 - The Angle Game
- 62 - Similar triangles
- 63 - Similar triangles (part 2)
- 64 - Angle Game (part 2)
- 65 - Acute Right and Obtuse Angles
- 66 - Area and Perimeter
- 67 - Circles: Radius, Diameter and Circumference
- 68 - Area of a circle
- 69 - The Pythagorean Theorem
- 70 - Pythagorean Theorem II
- 71 - 45-45-90 Triangles
- 72 - Intro to 30-60-90 Triangles
- 73 - 30-60-90 Triangles II
- 74 - Solid Geometry Volume
- 75 - Cylinder Volume and Surface Area
- 76 - Herons Formula
- 77 - Part 1 of Proof of Herons Formula
- 78 - Part 2 of the Proof of Herons Formula
- 79 - Inscribed and Central Angles
- 80 - Area of Inscribed Equilateral Triangle (some basic trig used)
- 81 - Right Triangles Inscribed in Circles (Proof)
- 82 - Area of Diagonal Generated Triangles of Rectangle are Equal
- 83 - Triangle Medians and Centroids
- 84 - Triangle Medians and Centroids (2D Proof)
- 85 - Rhombus Diagonals
- 86 - 2003 AIME II Problem 7
- 87 - Perpendicular Radius Bisects Chord
- 88 - Circumcenter of a Triangle
- 89 - Circumcenter of a Right Triangle
- 90 - Three Points Defining a Circle
- 91 - Point Line Distance and Angle Bisectors
- 92 - Incenter and incircles of a triangle
- 93 - Angle Bisector Theorem Proof
- 94 - Inradius Perimeter and Area
- 95 - Angle Bisector Theorem Examples
- 96 - Medians divide into smaller triangles of equal area
- 97 - Exploring Medial Triangles
- 98 - Proving that the Centroid is 2-3rds along the Median
- 99 - Median Centroid Right Triangle Example
- 100 - Proof - Triangle Altitudes are Concurrent (Orthocenter)
- 101 - Review of Triangle Properties
- 102 - Euler Line
- 103 - Eulers Line Proof
- 104 - Common Orthocenter and Centroid
- 105 - Quadrilateral Overview
- 106 - Proof - Opposite Sides of Parallelogram Congruent
- 107 - Proof - Diagonals of a Parallelogram Bisect Each Other
- 108 - Proof - Opposite Angles of Parallelogram Congruent
- 109 - Proof - Rhombus Diagonals are Perpendicular Bisectors
- 110 - Proof - Rhombus Area Half Product of Diagonal Length
- 111 - Area of a Parallelogram
- 112 - Problem involving angle derived from square and circle
- 113 - Area of a Regular Hexagon

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