Lines of Symmetry of Plane Shapes

Line of Symmetry

Here my dog "Flame" has her face made perfectly symmetrical with some photo editing.

The white line down the center is the Line of Symmetry

Folding Test

You can find if a shape has a Line of Symmetry by folding it.

Here I have folded a rectangle one way, and it didn't work.

So this is not a Line of Symmetry

But when I try it this way, it does work (the folded part sits perfectly on top, all edges matching):

So this is a Line of Symmetry

Triangles

A Triangle can have 3, or 1 or no lines of symmetry:

Equilateral Triangle (all sides equal, all angles equal)		Isosceles Triangle (two sides equal, two angles equal)		Scalene Triangle (no sides equal, no angles equal)
3 Lines of Symmetry		1 Line of Symmetry		No Lines of Symmetry

Quadrilaterals

Different types of Quadrilaterals (a 4-sided plane shape):

Square (all sides equal, all angles 90°)		Rectangle (opposite sides equal, all angles 90°)		Irregular Quadrilateral
4 Lines of Symmetry		2 Lines of Symmetry		No Lines of Symmetry

Kite		Rhombus (all sides equal length)
1 Line of Symmetry		2 Lines of Symmetry

Regular Polygons

A regular polygon has all sides equal, and all angles equal:

An Equilateral Triangle (3 sides)
has 3 Lines of Symmetry

A Square (4 sides)
has 4 Lines of Symmetry

A Regular Pentagon (5 sides)
has 5 Lines of Symmetry

A Regular Hexagon (6 sides)
has 6 Lines of Symmetry

A Regular Heptagon (7 sides)
has 7 Lines of Symmetry

A Regular Octagon (8 sides)
has 8 Lines of Symmetry

And the pattern continues:

• A regular polygon of 9 sides has 9 Lines of Symmetry
• A regular polygon of 10 sides has 10 Lines of Symmetry
• ...
• A regular polygon of "n" sides has "n" Lines of Symmetry

Circle

A line (drawn at any angle) that goes through its center is a Line of Symmetry.

So a Circle has infinite Lines of Symmetry.