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Summary
DescriptionDifferential change in area and radius of circle.svg
English: The yellow shaded portion resembles a rectangle of width dr. The length is somewhere between 2πr and 2π(r+dr). In most cases the area can be taken to be 2πdr in the limit that dr goes to zero. Integration of 2π(r+dr) from r=0 to r=R yields the area of a circle to be πR2.
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