Here mine dog "Flame" has actually her challenge made perfect symmetrical v a bitof picture magic.
The white line under the center is present of Symmetry
When the folded part sits perfectly on peak (all edges matching), then the fold line is a line of Symmetry.
Here I have folded a rectangle one way, and also it didn"t work.
But once I try it this way, it does work (the folded part sits perfectly on top, every edges matching):
Triangles
A Triangle have the right to have 3, or 1 or no present of symmetry:
 |  | |||
| Equilateral Triangle(all political parties equal, all angle equal) | Isosceles Triangle(two political parties equal, 2 angles equal) | Scalene Triangle(no sides equal, no angles equal) | ||
| 3 present of Symmetry | 1 heat of Symmetry | No present of Symmetry |
Quadrilaterals
Different varieties of quadrilateral (a 4-sided airplane shape):
 |  | |||
| Square(all sides equal, all angles 90°) | Rectangle(opposite political parties equal, all angle 90°) | Irregular Quadrilateral | ||
| 4 lines of Symmetry | 2 lines of Symmetry | No present of Symmetry |
 |  | |
| Kite | Rhombus(all sides same length) | |
| 1 line of Symmetry | 2 present of Symmetry |
Regular Polygons
A continual polygon has all political parties equal, and all angles equal:
| An Equilateral Triangle (3 sides) has 3 present of Symmetry | ||
| A Square (4 sides) has 4 lines of Symmetry | ||
 | A Regular Pentagon (5 sides) has 5 currently of Symmetry | |
 | A Regular Hexagon (6 sides) has 6 currently of Symmetry | |
 | A Regular Heptagon (7 sides) has 7 currently of Symmetry | |
 | A Regular Octagon (8 sides) has 8 currently of Symmetry |
And the pattern continues:
A regular polygon of 9 sides has actually 9 lines of SymmetryA continual polygon the 10 sides has actually 10 lines of Symmetry...A consistent polygon that "n" sides has "n" currently of SymmetryCircle |