Page 61 - Mathematics Class - IX
P. 61
6. Sector: The region between an arc and the two radii, joining the centre to the endpoints of the arc is called
a sector.
Like segments, you find that the minor arc corresponds to the minor sector and the major arc corresponds
to the major sector.
Major sector
O
Minor sector
P Q
7. Points for angle subtended by an arc:
l Congruent arcs of a circle subtend equal angles at the centre.
l The angle subtended by an arc at the centre is double the angle subtended by it at any point on the
circumference of the circle.
l Angles in the same segment of a circle are equal.
l If a line segment joining two points subtends equal angles at two other points lying on the same side of
the line containing the line segment, then the four points are concyclic.
PROCEDURE
1. Draw a circle on a coloured sheet with centre O as shown in Fig. (a).
2. Mark points A and B on its minor arc, point C on the other part of the circle as shown in Fig. (b).
C
O O
A B
Fig. (a) Fig. (b)
3. Join OA, OB, AC, BC as shown in Fig. (c).
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