The Radius of a sphere is 5 feet. find the area of the great circle of this sphere

Calculate the area of the great circle, if we substitute for r = 5, since only then the circuit will be the greatest.
$$\pi*r^2=3,14*5^2=78,5(ft^2)$$

$$The\ radius\ of\ a\ sphere\ is\ equal\ the\ radius\ of\ the\ great\ circle\ of\ this\ sphere\\\\R=5ft\\\\A_{O}=\pi R^2\Rightarrow A_O=\pi\times5^2=25\pi\ (ft^2)$$

2\pir=2*3.141*5=31.41m

2*pi*r=2*3.141*5=31.41m <- correct

2pi r is a circumference of the circle not area.

soryy: pi * r^2 = 3,14 * 5^2 = 78,5 (ft^2)

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