1. Line Symmetry 5 7 2 1 © 2004 All rights reserved
Courtesy of Whiteboardmaths.com

2. 1 LoS One Line of Symmetry Vertical lines of symmetry
Horizontal lines of symmetry
Diagonal lines of symmetry

3. 2 Lines of Symmetry
2 LoS

4.  Rectangle The Rectangle Problem
A rectangle has only 2 lines of symmetry and not 4 like the square 
To see this consider the following:
Mirror Line
Half a rectangle

5.  The Rectangle Problem
A rectangle has only 2 lines of symmetry and not 4 like the square 
To see this consider the following:
Half a rectangle
Mirror Line
A reflection in the diagonal would produce a kite!

6. 3 LoS
3 Lines of Symmetry

7. 4 LoS
4 Lines of Symmetry

8. 5 Lines of Symmetry
5 LoS

9. 6 LoS
6 Lines of Symmetry

10. Regular Regular Polygons Equilateral Triangle Square Regular Pentagon
Regular polygons have lines of symmetry equal to the number of sides/angles that they possess.
Regular
Regular Hexagon
Regular Octagon

11. How many lines of symmetry for each shape?4 3 6
Mix 1 5 8

12. How many lines of symmetry for each shape?6 5 3
Mix 2 4 5