Page 248 - Ganit Kaushal

side of the line of symmetry, as shown in the given figures. The dotted lines are the lines of symmetry or the
mirror lines, where we assume the mirrors are being placed. The figures on both sides of the mirror line are

symmetrical, or say identical. Such a symmetry is called Reflection Symmetry.
After understanding the whole concept of symmetry, we can say that:

‘Conceptually, linear symmetry, mirror symmetry and reflection symmetry are one and the same concepts.’

Remember

1. Mathematically, symmetry means that one shape becomes exactly like another when you move it in
some way – flip it, slide it or turn it.
2. Line symmetry, mirror symmetry or reflection symmetry occurs when an object is reflected
across a line, like looking in a mirror. A line of symmetry splits a figure in half so that each part is
exactly the same. The line of symmetry does not have to be vertical or horizontal only, it can go in any
direction. A symmetrical figure can have any number of lines of symmetry.

Plane Shapes and their Lines of Symmetry

Different shapes can have different numbers of lines of symmetry or no lines of symmetry at all. The following
figures show some standard plane shapes and the number of lines of symmetry they have. Dotted lines show
their lines of symmetry.

1. Shapes with no line of symmetry:

Scalene triangle The digit 7 Quadrilateral The letter F

2. Shapes with one line of symmetry:

Isosceles triangle Kite The digit 3 The letter A

3. Shapes with two lines of symmetry:

Rectangle Rhombus The digit 0

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