Question

(a) let r be the radius of a sphere. write an expression for the exact surface area of a sphere.

Explanation:

Step1: Recall surface - area formula

The formula for the surface area of a sphere with radius \(r\) is well - known.
The surface area \(A\) of a sphere is given by \(A = 4\pi r^{2}\).

Answer:

\(4\pi r^{2}\)