hemisphere.
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The surface area of a semicircle has the round surface which is half a sphere and also has the flat surface which is a circle.
A hemisphere has 1 circular face and one which is half the surface of a sphere.
Surface area of half a sphere = 2*pi*radius2 Surface area = 200*pi = 628.3185307 square units.
To do this question, we have to ask ourself, what formula do you use to find the surface area of a sphere. The answer should be known to you, but it is 4πr2. Since we know how to find the surface area for a full sphere, then finding the surface for a half sphere is just half the job. You use the formula for the full sphere 4πr2, and divide it by 2... so (4πr2) / 2 . Voila!
Find the surface area of the full sphere [ A = 4 pi R2 ] and then take half of it. You wind up with [ 2 pi R2 ] for the outside surface area of a half sphere, or [ 4 pi R2 ] for the (inside + outside) surface area of the half sphere. (Since the inside and outside are now both exposed to the weather, you probably want to paint both surfaces.)