A line of symmetry is a line that cuts a shape exactly in half. This means that if you were to fold the shape along the line, both halves would match exactly. Equally, if you were to place a mirror along the line, the shape would remain unchanged. If all the sides and angles of a polygon are equal then it is said to be a regular polygon. Like the equilateral triangle, square etc. All the regular polygons are symmetrical shapes. In the regular polygon, the number of lines of symmetry is the same as the number of its sides