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How do you do area of sector

Area of sector JFK=70degree JD=7cm

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Eric Y. | SAT PrepSAT Prep
5.0 5.0 (5 lesson ratings) (5)
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A sector is some portion of a circle.
Formula for area of a circle is A =(pi)r2
 
For the area of some sector with x degrees lets use a proportional relationship
 
Areasector               x degrees
____________   =       _____________
 
Areacircle                  360 degrees
 
(AREAsector)  = 70   
(pi) r2                  360
 
Solve by cross multiplication.
Patricia S. | Math Tutoring for K-12 & CollegeMath Tutoring for K-12 & College
5.0 5.0 (39 lesson ratings) (39)
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Hi, Abby!
 
A sector is simply a piece of a circle.  The easiest way to find the area of a sector is to find the area as if it were a complete circle (Area of a circle is pi*r2.) and then multiply it by a ratio to represent the size of the sector compared to a whole circle (degree/360).
 
In your question, where JFK = 70 degrees and JD = 7cm, I am going to assume that JD is the diameter of what would be the whole circle (If it is the radius, then you can just use 7 for r).
 
radius = r = 1/2 * diameter = 1/2 * 7 = 3.5
 
Area = pi * r2 * (degrees/360)
Area = 3.14 * (3.5)2 * (70/360)
Area = 3.14 * 12.25 * 70/360
Area = 7.48 cm2
 
Hope this helps!
 
Patty