Free geometry lessons

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

Prerequisites

1. Basic geometry
2. Parallel planes
3. Types of angles
4. Perpendicular bisector
5. Angle bisector
6. Find angle measures
7. Complementary and supplementary angles
8. Types of polygons
9. Convex polygons
10. Concave polygons
11. Sum of all exterior angles of a polygon
12. Types of triangles
13. Types of quadrilaterals
14. Relationships among special quadrilaterals
15. Solid figures
16. Properties of parallelograms
17. Isometric drawing
18. Orthographic drawing
    
19. Tangent circles
20. Concentric circles
21. Inscribed and circumscribed circles

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 rhombus
15. Area of a trapezoid
16. Area of irregular shapes
17. Area of a circle
18. Area of a sector
19. Area of a regular polygon
20. Area of a triangle given sas
21. Heron's formula
22. 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. How to find the midpoint of a line segment
4. How to find the endpoint of a line segment
5. 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

Side-splitter theorem

Angle bisector theorem

Area between four touching circles

Optical illusions with geometry

Cavalieri's principle

Locus in geometry

How to test for symmetry

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