Fold paper shapes in half. Do the two halves match? If yes, that fold is a line of symmetry.
Lines of symmetry
- Square — 4 (two diagonals + horizontal + vertical)
- Rectangle — 2 (horizontal + vertical)
- Equilateral triangle — 3
- Circle — infinite
- Scalene triangle — 0
Regular polygons of n sides always have exactly n lines of symmetry. Asymmetric shapes have zero.