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Chapter - 15

Symmetry

Lines of symmetry : - Whenever a figure is divided into two congruent parts by a straight line, then the line is called line of symmetry and the figure is said to be symmetrical about the line.

In the adjoining figure, ABCD is a rectangle and its lines of symmetry are PQ and RS.

If in the following figures if these are folded along the dotted line, one half of these coincides with other half.

We see that each of of the above figure are divided into two cougruent parts by the dotted lines, which are their lines of symmetry.