Free geometry lessons

A great variety of free geometry lessons. First start studying the prerequisites.

Reasoning and Proof

  1. Conditional statement
  2. Converse of a conditional statement
  3. Truth value of a conditional statement

Perimeter and Area of Shapes

  1. Perimeter of shapes
  2. Perimeter of a square
  3. Perimeter of a rectangle
  4. Perimeter of a triangle
  5. Perimeter of a trapezoid
  6. Perimeter of a circle
  7. Perimeter in the coordinate system
  8. Perimeter formulas
  9. Perimeter word problems
  10. Area of shapes
  11. Area of triangles
  12. Area of an equilateral triangle
  13. Area of a kite
  14. Area of a trapezoid
  15. Area of irregular shapes
  16. Area of a circle
  17. Area of a sector
  18. Area of a regular polygon
  19. Heron's formula
  20. Heron's formula calculator    

The circle 

  1. Introduction to the circle
  2. How to find the number pi
  3. Circumference of a circle
  4. Find the radius of a circle given the circumference
  5. Area of a circle
  6. How to approximate the area of a circle

Volume and Surface Area of Shapes

  1. Volume of solids
  2. Volume of a cube
  3. Volume of a box
  4. Volume of a sphere
  5. Volume of an ellipsoid
  6. Volume of a cylinder
  7. Volume of a cone
  8. Volume of a pyramid
  9. Volume of irregular shapes
  10. Difference between volume and capacity
  11. Volume formulas
  12. Finding surface area
  13. Surface area of a cube
  14. Surface area of a rectangular prism
  15. Surface area of a cylinder
  16. Surface area of a square pyramid
  17. Surface area of a sphere
  18. Surface area of a cone
  19. Surface area formulas 

Congruence and Similarity

  1. Congruent shapes
  2. Congruent triangles
  3. Properties of congruence
  4. Similar shapes
  5. Similar triangles

Transformations

  1. Types of transformations in geometry
  2. How to find a translation image
  3. How to find a reflection image

Slope and standard form of a line

  1. What is slope
  2. How to find the slope
  3. Undefined slope
  4. Graphing slope
  5. Slope intercept form
  6. Point slope form
  7. Find slope using slope-intercept form
  8. Slope calculator

Pythagorean theorem

  1. Pythagorean theorem
  2. Converse of the Pythagorean theorem
  3. Pythagorean triples
  4. Special right triangles
  5. Pythagorean word problems
  6. Pythagorean theorem calculator

Geometric formulas

  1. Distance formula
  2. Centroid of a triangle
  3. Midpoint of a line segment
  4. Common geometry formulas

Construction in geometry

  1. Straightedge and compass construction
  2. Tessellations in geometry
  3. Line symmetry
  4. Order of rotational symmetry

Analytic Geometry

  1. Inclination of a line
  2. Angle between two lines
  3. Equation of a circle
  4. Derive the equation of a parabola
  5. Derive the equation of an ellipse
  6. Distance between a point and a line

Word problems in geometry

Math problem solving strategies

Common mistakes in math

Geometry word problems

Perimeter word problems

Area word problems


Interesting topics
Geometry proofs

Geometry postulates

Segment addition postulate

Angle bisector theorem

Area between four touching circles

Optical illusions with geometry

Cavalieri's principle

Locus in geometry

How to test for symmetry

What we want to achieve with these geometry lessons

Goal:

  • Identify basic shapes in geometry
  • Find perimeter and area of shapes
  • Find volume and surface area of solids
  • Learn about congruency
  • Find and graph the slope
  • Find the standard from of a line
  • Solve word problems in geometry
  • Explore some important proofs in geometry
  • And more!
Geometric formulas

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