This formula can be compared with the area of a triangle. R2 x2 y2. The area formula is intuitive.
Or when you know the Diameter.
Alternatively one can define a conic section purely in terms of plane geometry. The exact formula is p r 2 314 r 2 The formula 3r 2 is indeed a very good approximation A little word problem about approximating the area of a circle Approximate the area of a circle whose diameter is equal to 4 cm. Visual on the figure below. Radius and height the area of the base plus the area of the lateral surface.