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Geometry Course Videos from The Khan Academy
Click on the links below to view specific geometry video lessons.
- Euclid as the Father of Geometry
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- Language and Notation of Basic Geometry
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- Lines, Line Segments, and Rays
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- Language and Notation of the Circle
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- Angle Basics
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- Measuring Angles in Degrees
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- Using a Protractor
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- Measuring Angles
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- Complementary and Supplementary Angles
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- Angles at the intersection of two lines
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- Proof-Vertical Angles are Equal
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- Angles Formed by Parallel Lines and Transversals
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- Proof - Sum of Measures of Angles in a Triangle are 180
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- Triangle Angle Example 1
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- Triangle Angle Example 2
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- Triangle Angle Example 3
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- Challenging Triangle Angle Problem
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- Proof - Corresponding Angle Equivalence Implies Parallel Lines
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- Finding more angles
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- Sum of Interior Angles of a Polygon
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- Congruent Triangles and SSS
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- SSS to Show a Radius is Perpendicular to a Chord that it Bisects
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- Other Triangle Congruence Postulates
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- Two column proof showing segments are perpendicular
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- Sum of the exterior angles of convex polygon
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- Finding Congruent Triangles
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- More on why SSA is not a postulate
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- Congruent Triangle Proof Example
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- Congruent Triangle Example 2
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- Congruent legs and base angles of Isosceles Triangles
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- Equilateral Triangle Sides and Angles Congruent
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- Equilateral and Isosceles Example Problems
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- Another Isosceles Example Problem
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- Example involving an isosceles triangle and parallel lines
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- Figuring out all the angles for congruent triangles example
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- Perimeter and Area Basics
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- Triangle Area Proofs
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- Interesting Perimeter and Area Problems
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- Koch Snowflake Fractal
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- Area of an Equilateral Triangle
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- Area of Koch Snowflake (part 1) - Advanced
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- Area of Koch Snowflake (part 2) - Advanced
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- Challenging Perimeter Problem
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- Similar Triangle Basics
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- Similarity Postulates
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- Similar Triangle Example Problems
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- Similarity Example Problems
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- Challenging Similarity Problem
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- Similarity example where same side plays different roles
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- Finding Area Using Similarity and Congruence
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- Pythagorean Theorem Proof Using Similarity
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- 30-60-90 Triangle Side Ratios Proof
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- 45-45-90 Triangle Side Ratios
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- 30-60-90 Triangle Example Problem
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- The Golden Ratio
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- Introduction to angles (old)
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- Angles (part 2)
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- Angles (part 3)
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- Angles formed between transversals and parallel lines
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- Angles of parallel lines 2
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- The Angle Game
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- Similar triangles
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- Similar triangles (part 2)
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- Angle Game (part 2)
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- Acute Right and Obtuse Angles
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- Area and Perimeter
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- Circles: Radius, Diameter and Circumference
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- Area of a circle
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- The Pythagorean Theorem
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- Pythagorean Theorem II
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- 45-45-90 Triangles
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- Intro to 30-60-90 Triangles
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- 30-60-90 Triangles II
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- Solid Geometry Volume
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- Cylinder Volume and Surface Area
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- Heron's Formula
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- Part 1 of Proof of Heron's Formula
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- Part 2 of the Proof of Heron's Formula
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- Inscribed and Central Angles
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- Area of Inscribed Equilateral Triangle (some basic trig used)
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- Right Triangles Inscribed in Circles (Proof)
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- Area of Diagonal Generated Triangles of Rectangle are Equal
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- Triangle Medians and Centroids
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- Triangle Medians and Centroids (2D Proof)
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- Rhombus Diagonals
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- 2003 AIME II Problem 7
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- Perpendicular Radius Bisects Chord
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- Circumcenter of a Triangle
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- Circumcenter of a Right Triangle
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- Three Points Defining a Circle
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- Point Line Distance and Angle Bisectors
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- Incenter and incircles of a triangle
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- Angle Bisector Theorem Proof
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- Inradius Perimeter and Area
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- Angle Bisector Theorem Examples
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- Medians divide into smaller triangles of equal area
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- Exploring Medial Triangles
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- Proving that the Centroid is 2-3rds along the Median
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- Median Centroid Right Triangle Example
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- Proof - Triangle Altitudes are Concurrent (Orthocenter)
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- Review of Triangle Properties
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- Euler Line
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- Euler's Line Proof
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- Common Orthocenter and Centroid
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- Quadrilateral Overview
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- Proof - Opposite Sides of Parallelogram Congruent
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- Proof - Diagonals of a Parallelogram Bisect Each Other
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- Proof - Opposite Angles of Parallelogram Congruent
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- Proof - Rhombus Diagonals are Perpendicular Bisectors
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- Proof - Rhombus Area Half Product of Diagonal Length
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- Area of a Parallelogram
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- Problem involving angle derived from square and circle
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- Area of a Regular Hexagon
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