Question

what is a sector in a circle

Answer 1

Suppose you have and arc AB on a circle with centre O
You join AO and BO.
No you have a Δular figure which looks like a slice of pizza or pie
This is called a Sector; more specifically a Minor Sector. The leftover part is also a Sector; the Major Sector.

SO, formally, Sector is the area enclosed by an arc and two radii.

In my figure, the red portion is the minor sector.
hope this helped

Answer 2

 sector in a circle is define as the ares covered or enclosed by 2 radii of an circle and 1 arc
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there are 2 types of sector 
1)minor sector
2)major sector 
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if the area or the angle enclosed or covered by an sector is small , it is called as a minor sector , it is the smaller portion


if the area or the angle enclosed or covered by an sector is large, it is called as a minor sector , it is the larger portion
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