You can use an interactive ellipses to approximate curves. If you use a parent function of an ellipse as shown at the bottom left and have the coordinates (h,k+b) and (h+a,k) you can make a scalable ellipse that you can drag to match curves. You can also plot (h,k) as the center of the ellipse and use it to move the ellipse without changing the sides. Make sure the (h,k+b) can only move vertically and the (h+a,k) can only move horizontally by clicking into the circle to the l

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