Area of an Ellipse

Figure 1

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You know the formula for the area of a circle of radius R. It is Pi*R².

But what about the formula for the area of an ellipse of semi-major axis of length A and semi-minor axis of length B? For example:

(x²/A²) + (y²/B²) = 1.

The area of such an ellipse is

Area = Pi * A * B ,

a very natural generalization of the formula for a circle!