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Lines of Symmetry

This topic deals with drawing shapes with lines of symmetry and finding the number of lines of symmetry in a figure. This topic also covers determining whether a figure has rotational symmetry.

Topic: Identify Lines of Symmetry

  • The figure has line symmetry if it can be folded or reflected so that the two parts of the figure match

  • Even if two figures are congruent, they may not be symmetrical. They will be symmetrical only if the two parts of the figure match after being folded or reflected

  • The line of reflection is called the line of symmetry

  • Irregular figures do not have a line of symmetry

Topic: Drawing Lines of Symmetry

  • The line that separates the figure into two matching halves, is called a line of symmetry

  • Irregular figures do not have a line of symmetry

Topic: Rotational Symmetry

  • All figures, when rotated by 360° (or a full turn), will look exactly the same as they did before being turned

  • Some figures will look the same at certain angles of rotation which are less than 360° (90°, 180°, 270°). Such figures have rotational symmetry
    For example, the figure of a square reappears in the same position as it is turned 90°, 180°, 270°, and 360°
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