An item is regularly priced at 20$ . Hong bought it at a discount of 65% off the regular price . how much did Hong pay ?
1 answer:
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Presumably you should be doing this using calculus methods, namely computing the surface integral along 
.
But since describes a sphere, we can simply recall that the surface area of a sphere of radius 
is 
.
In calculus terms, we would first find an expression for the surface element, which is given by
So the area of the surface is
as expected.
But since
In calculus terms, we would first find an expression for the surface element, which is given by
So the area of the surface is
as expected.