Free geometry lessons

Prerequisites

1. Basic geometry
2. Types of angles
3. Complementary and supplementary angles
4. Types of polygons
5. Convex polygons
6. Concave polygons
7. Sum of all exterior angles of a polygon
8. Types of triangles
9. Types of quadrilaterals
10. Relationships among special quadrilaterals
11. Solid figures
12. Properties of parallelograms
13. Isometric drawing
14. Tangent circles
15. Concentric circles
16. Inscribed and circumscribed circles

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 formulas
8. Perimeter word problems
9. Area of shapes
10. Area of triangles
11. Area of an equilateral triangle
12. Area of a kite
13. Area of a trapezoid
14. Area of irregular shapes
15. Area of a circle
16. Area of a sector
17. Area of a regular polygon
18. Heron's formula
19. 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. Similar shapes
4. 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. 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

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

Geometric calculator

 Geometry calculator

Word problems in geometry

Math problem solving strategies

Common mistakes in math

Geometry word problems

Perimeter word problems

Area word problems

Interesting topics
Direct variation

Geometry proofs

Geometry postulates

Segment addition postulate

Area between four touching circles

Optical illusions with geometry

Cavalieri's principle

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Geometry lessons

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