Answer:
r = √A/4π
Step-by-step explanation:
[tex]A=4\pi r^2\\\frac{A}{4\pi }=r^2\\\sqrt{\frac{A}{4\pi } }=r[/tex]
r = √(A/4π)
A = 4πr^2
Divide both sides by 4π
r^2 = A/4π
Take square root of both sides.
We take the positive square root only as r must be positive.
