Answer :

konrad509
[tex]A=4\pi=\pi r^2\\ 4\pi=\pi r^2\\ r^2=4\\ r=2\\\\ d=2r\\ d=2\cdot2\\ d=4[/tex]
apologiabiology
area=pi times radius^2 so

if area=4pi=pi times r^2
4 times pi=r^2 times pi
divide both sdies by pi
4=r^2
square root
2=radius since legnth cannot be negative

radius=1/2 diamters
2 radius=diameter
2(2)=diameter=4
diameter=4

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