4. A FIGURE HAS LINE SYMMETRY IF
A LINE CAN BE DRAWN DIVIDING
THE FIGURE INTO TWO
IDENTICAL PARTS. THE LINE IS
CALLED A LINE OF SYMMETRY. A
FIGURE MAY HAVE NO LINE OF
SYMMETRY, ONLY ONE OF
SYMMETRY, TWO LINES OF
SYMMETRY OR MULTIPLE LINES
OF SYMMETRY.
Line Symmetry
17. Rotational Symmetry
If, after a rotation, an object looks exactly the same,
we say that it has a rotational symmetry.
• This fixed point is the centre of rotation .
• The angle by which the object rotates is the angle of
rotation.
• A half-turn means rotation by 180 degree; a quarter-
turn means rotation by 90 degree. Rotation may be
clockwise or anticlock wise.
• In a complete turn ( of 360 degree ), the number of
times an object looks exactly the same is called the
order of rotational symmetry.