Determining the expressions for the surface area of a sphere requires a more detailed analysis, so we will not discuss those here. Instead, for now you are expected to simply memorize these expressions:

SA of sphere = \(4\pi {r^2}\)

Curved SA of hemisphere = \(2\pi {r^2}\)

Flat SA of hemisphere = \(\pi {r^2}\)

Total SA of hemisphere= \(\left\{ \begin{array}{l} 2\pi {r^2} + \pi {r^2}\\ 3\pi {r^2} \end{array} \right.\)
Example 1: Find the surface area of a sphere of radius 5 cm.
Solution: We have:
\[\begin{align}&SA = 4\pi {r^2} \approx 314\,{\rm{c}}{{\rm{m}}^2}\end{align}\]
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