# Geometry

Geometry is all about **shapes** and their properties.

If you like playing with objects, or like drawing, then geometry is for you!

Geometry can be divided into:

**Plane Geometry** is about flat shapes like lines, circles and triangles ... shapes that can be drawn on a piece of paper

**Solid Geometry** is about three dimensional objects like cubes, prisms, cylinders and spheres.

Hint: Try drawing some of the shapes and angles as you learn ... it helps. |

## Point, Line, Plane and Solid

A Point has no dimensions, only position

A Line is one-dimensional

A Plane is two dimensional (2D)

A Solid is three-dimensional (3D)

## Why?

Why do we do Geometry? To discover patterns, find areas, volumes, lengths and angles, and better understand the world around us.

## Plane Geometry

Plane Geometry is all about shapes on a flat surface (like on an endless piece of paper).

- Quadrilaterals (Rhombus, Parallelogram, etc)
- Rectangle, Rhombus, Square, Parallelogram, Trapezoid and Kite
- Interactive Quadrilaterals
- Parallelogram In Any Quadrilateral
- Paper Sizes
- Shapes Freeplay

### Polygons

A Polygon is a 2-dimensional shape made of straight lines. Triangles and Rectangles are polygons.

Here are some more:

### The Circle

- Circle
- Pi
- Circle Area by Lines
- Circle Sector and Segment
- Circle Area by Sectors
- Activity: Dropping a Coin onto a Grid
- Arc
- Annulus

Circle Theorems (Advanced Topic)

### Symbols

There are many special symbols used in Geometry. Here is a short reference for you:

### Congruent and Similar

### Angles

## Using Drafting Tools |

### Transformations and Symmetry

### Coordinates

## More Advanced Topics in Plane Geometry

### Pythagoras

### Conic Sections

### Circle Theorems

- Circle Theorems
- Tangent and Secant Lines
- Intersecting Secants Theorem
- Intersecting Chords Theorem
- Angle of Intersecting Secants Theorem

## Trigonometry

Trigonometry is a special subject of its own, so you might like to visit:

## Solid Geometry

Solid Geometry is the geometry of three-dimensional space - the kind of space we live in ...

... let us start with some of the simplest shapes:

### Polyhedra and Non-Polyhedra

There are two main types of solids, "Polyhedra", and "Non-Polyhedra":

Polyhedra *(they must have flat faces)*:

Cubes and Cuboids (Volume of a Cuboid) | |

Platonic Solids | |

Prisms | |

Pyramids |

Non-Polyhedra *(when any surface is not flat)*:

Sphere | Torus | |||

Cylinder | Cone |

- Polyhedron Models
- Volume and Area of a Sphere Calculator
- Spheroid
- Cross Sections
- Vertices, Faces, and Edges
- Cone vs Sphere vs Cylinder
- Pyramid vs Cone
- Prism vs Cylinder
- Volume of Horizontal Cylinder
- Euler's Theorem
- Pythagoras in 3D