Sphere Formula Area Proof. And sum the area of all the shaded portions as t → 0 noting that δt = rδθ. Or more directly a = ∫2πrt = 02rdt.

$\dfrac 1 3 \pi \paren {2 a}^2 2 a$ the. Now, surface area of sphere = 4 π r 2, so after substituting the value of r = 8, we get,.