To find the area of a circle given its circumference \( C \), we can use the following relationships:
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The formula for the circumference of a circle is: \[ C = 2\pi r \] where \( r \) is the radius of the circle.
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The formula for the area of a circle is: \[ A = \pi r^2 \]
Given that the circumference \( C = 4\pi \), we can use the circumference formula to solve for the radius \( r \):
\[ 4\pi = 2\pi r \]
Dividing both sides by \( 2\pi \):
\[ r = \frac{4\pi}{2\pi} = 2 \]
Now that we know the radius \( r \), we can substitute it back into the area formula:
\[ A = \pi r^2 = \pi (2^2) = \pi \cdot 4 = 4\pi \]
Thus, the area of the circle is:
\[ \boxed{4\pi} \]