Plane Geometry - Math Is Fun

Plane Geometry

If you like drawing, then geometry is for you!

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

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)

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

• 2D Shapes
• Activity: Sorting Shapes
• Triangles
• Right Angled Triangles
• Interactive Triangles

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

• Perimeter

• Area
• Area of Plane Shapes
• Area Calculation Tool
• Area of Polygon by Drawing
• Activity: Garden Area

• General Drawing Tool
• Square Calculator and Rectangle Calculator

Polygons

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

Here are some more:

Pentagon

Pentagram

Hexagon

• Properties of Regular Polygons
• Diagonals of Polygons
• Interactive Polygons

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:

Geometric Symbols

Congruent and Similar

• Congruent Shapes
• Similar Shapes

Angles

Types of Angles

Acute Angles

Right Angles

Obtuse Angles

Straight Angle

Reflex Angles

Full Rotation

Degrees (Angle) Radians Congruent Angles Parallel Lines and Pairs of Angles Transversal Adjacent Angles A Triangle Has 180° Supplementary Angles Complementary Angles

Angles Around a Point Angles on a Straight Line Interior Angles Exterior Angles Interior Angles of Polygons Exterior Angles of Polygons

Using Drafting Tools

• Geometric Constructions
• Using the Protractor
• Constructing Triangles
• Using the Drafting Triangle and Ruler
• Using a Ruler and Compass

Transformations and Symmetry

Transformations:

• Rotation
• Reflection
• Translation
• Resizing

Symmetry:

• Reflection Symmetry
• Rotational Symmetry
• Point Symmetry
• Lines of Symmetry of Plane Shapes

• Symmetry Artist

• Activity: Symmetry of Shapes
• Activity: Make a Mandala
• Activity: Coloring (The Four Color Theorem)

• Tessellations
• Tessellation Artist

Coordinates

• Cartesian Coordinates
• Interactive Cartesian Coordinates
• Hit the Coordinate Game

More Advanced Topics in Plane Geometry

Pythagoras

• Pythagoras' Theorem
• Pythagorean Triples

Conic Sections

• Set of all points
• Conic Sections
• Eccentricity
• Ellipse
• Parabola and Projectile Animation
• Hyperbola

Circle Theorems

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

Triangle Centers

Trigonometry

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

• Introduction to Trigonometry
• Trigonometry Index

Geometry Index