Page 169 - ICSE Math 7

Interior angles n

The four angles formed between two straight lines intersected by a transversal 2 1
3
are known as interior angles. In the given figure, angles 3, 4, 5 and 6 are 4 l
interior angles.
6 5 m
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n
Exterior angles
2 1
The four angles formed that are not in the region or the space between two 3
straight lines intersected by a transversal are known as exterior angles. In 4 l
the given figure, angles 1, 2, 7 and 8 are exterior angles. 6 5 m

7 8

Co-interior angles n
2 1
The pair of interior angles which are on the same side of the transversal 3
are known as co-interior angles or allied angles. In the given figure, angles 4 l
3 and 6, and angles 4 and 5 are two pairs of co-interior angles.
6 5 m
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n
Exterior allied angles
2 1
The pair of exterior angles which are on the same side of the transversal are 3
known as exterior allied angles. In the given figure, two pairs of exterior 4 l
allied angles are angles 1 and 8, and angles 2 and 7.
6 5 m
7 8

Alternate angles n
The pair of angles formed on opposite sides of the transversal are known 2 1
as alternate angles. Both these angles are either exterior or interior, but not 3 4 l
adjacent. In the given figure, angles 3 and 5, and angles 4 and 6 are two
pairs of alternate interior angles, and angles 1 and 7 and angles 2 and 8 6 5 m
are two pairs of alternate exterior angles. 7 8

Corresponding angles n
Corresponding angles are two non-adjacent angles made by the intersection 2 1
of two lines by a transversal. One of the corresponding angles is interior 3 4 l
and the other is exterior, and both the angles are on the same side of the
transversal. In the given figure, the four pairs of corresponding angles are 6 5 m
1 and 5, 4 and 8, 2 and 6 and 3 and 7. 7 8

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