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 do we do Geometry? To discover patterns, find areas, volumes, lengths and angles, and better understand the world around us.
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
A Polygon is a 2-dimensional shape made of straight lines. Triangles and Rectangles are polygons.
Here are some more:
- Circle Area by Lines
- Circle Sector and Segment
- Circle Area by Sectors
- Activity: Dropping a Coin onto a Grid
Circle Theorems (Advanced Topic)
There are many special symbols used in Geometry. Here is a short reference for you:
Congruent and Similar
Types of Angles
Using Drafting Tools
Transformations and Symmetry
More Advanced Topics in Plane Geometry
- Circle Theorems
- Tangent and Secant Lines
- Intersecting Secants Theorem
- Intersecting Chords Theorem
- Angle of Intersecting Secants Theorem
Trigonometry is a special subject of its own, so you might like to visit:
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:
Common 3D Shapes
Polyhedra and Non-Polyhedra
There are two main types of solids, "Polyhedra", and "Non-Polyhedra":
Polyhedra (they must have flat faces):
of a Cuboid)
Non-Polyhedra (when any surface
is not flat):
- Polyhedron Models
- Volume and Area of a Sphere Calculator
- 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