Answers

2016-01-30T00:41:01+05:30
Hope that u will get it
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dθ : 2π = dA : πr^2 
then 
dA=dθ*πr^2/(2π) 
dA=1/2r^2dθ 
A=ΣdA = 1/2r^2∫dθ
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