The area a of a sector of a circle is given by a=nr2s/360

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I'm not terrible certain I know what you are trying to do here. The question is not clear.  Maybe if I give an example of how to use the formula, it make clear what the formula does. Below is a diagram. Label the ends of the circle's radii as A and B. Label the center of the circle as O. 

The sector of the circle is AOB. The area is that which is inside AOB. The formula you have quoted is for the region inside AOB. The n should be a pi. They look very much alike.

The s should be an angle in degrees. It is angle <AOB. Let us see how the area can be found

Suppose the Givens are
π = 3.14
S = 150°
r = OA = 10

What is the Area of such a sector?  
Area = π r² s/360
Area = π 10² 150/360
Area = π 100 * 150 / 360
Area = π 15000 / 360
Area = π 41.667 Sometimes this is the answer, and sometimes they want a decimal amount
Area = 3,14 * 41.667
Area = 130.8997 is the decimal amount.

The area of a circle = π r² = 100 * π 
The decimal amount of the Area of the circle = 100 * 3.14 = 314
Notice that the area of the circle is bigger than the sector. Isn't that the way it should be?

So what do you need to find the area of a sector? You need
1. The radius.
2. Pi
3. The measurement of the central angle.