angles separately, the child understands fact that the two angles add up to a straight
angle thus making the two angles supplement to each other.
- Linear pair
If the sum of two adjacent angles is equal to 180o or a straight angle then the two
angles are said to form a linear pair.
The procedure followed in teaching the idea of supplementary angles may be followed
to teach the idea of linear pair also.
- Bisector of an angle
A ray which divides an angle into two equal halves is called the bisector of the angle.
The idea may be taught through paper folding. Take a neatly cut paper which forms a
right angle at its vertices. Select any one vertex and fold the paper to form a crease
which divides the angle formed at the vertex into two. Since the right angle formed at
the vertex is now divided into two by the crease formed, to make angles of 45o on
either side of it, the line formed by the crease formed is the angle bisector.
The child must be explained to understand that bisection means dividing exactly into
two halves. Also the difference between intersection and bisection - that intersection
is just dividing and bisection denotes dividing exactly into two halves, should be
described to the child.
- Adjacent angles
Two angles having a common arm and the same vertex are said to be adjacent angles.
Here OB is a common arm for the angles AOB and BOC, hence they are adjacent
angles.
A^600 C
B
O
