Answer:
A = (1/2)Cr
Explanation:
You're supposed to observe that the circle area decomposes into what is approximately* a parallelogram with height equal to the circle radius and base equal to half the circumference. The area is then ...
A = bh
A = (1/2)Cr
If you fill in the formula for C, you find this matches the formula for the area of a circle:
A = (1/2)(2πr)(r) = πr²
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* In the limit, as the number of sectors approaches infinity, this is exactly a parallelogram.