21/49 in simplist from would be 3/7.
Your answer is <em>3/7</em>
The surface element is
and the integral is
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To compute the last integral, you can integrate by parts:
For this integral, consider a substitution of
and the result above follows.
The exact name of the postulate isn't coming to mind, but it's the postulate that any three points that are not on the same line will form a unique plane. A plane in mathematics is a flat surface that extends in all directions.
The answer would be A: R= C over 2 pi
Hope this helps :)