High school geometry

About Course

Learn high school geometry for free—transformations, congruence, similarity, trigonometry, analytic geometry, and more. Full curriculum of exercises and videos. This is the property of khanacademy.org and is available for free on their website.

Topics for this course

282 Lessons

Geometry foundations

Intro to Euclidean geometry
Euclid as the father of geometry
Terms & labels in geometry
Lines, line segments, & rays
Specifying planes in three dimensions
Geometric definitions example
Measuring angles in degrees
Measuring angles using a protractor
Measuring angles using a protractor 2
Acute, right, & obtuse angles
Vertical angles
Equation practice with vertical angles
Complementary & supplementary angles
Equation practice with complementary angles
Equation practice with supplementary angles
Angles, parallel lines, & transversals
Parallel & perpendicular lines
Missing angles with a transversal
Measures of angles formed by a transversal
Proving angles are congruent
Angles in a triangle sum to 180° proof
Triangle exterior angle example
Worked example: Triangle angles (intersecting lines)
Worked example: Triangle angles (diagram)
Triangle angle challenge problem 2
Sum of interior angles of a polygon
Sum of the exterior angles of a polygon
Triangle inequality theorem
Intro to quadrilateral
Quadrilateral properties
Kites as a geometric shape
Quadrilateral types
Proof: Opposite sides of a parallelogram
Proof: Opposite angles of a parallelogram
Perimeter & area
Area of a triangle
Area of a parallelogram
Area of trapezoids
Area of kites
Area of a triangle on a grid
Area of a quadrilateral on a grid
Area of composite shapes
Perimeter & area of composite shapes
Challenge problems: perimeter & area
Radius, diameter, circumference & π
Area of a circle
Radius & diameter from circumference
Area of a circle intuition
Intro to nets of polyhedra
Surface area using a net: rectangular prism




Right triangles & trigonometry

Solid geometry

Analytic geometry


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