This paper presents an alternative derivation of the perimeter formula of an ellipse by combining projection and calculus. It offers a different perspective compared to traditional integration methods. The purpose of this paper is to illustrate the geometrical properties of ellipses. In addition, it further develops the projection method to obtain a summation approximation based on projection, with an O (x^-4) convergence rate and a relative error mostly independent of the eccentricity when e is not near 1, which is proved rigorously via asymptotic error analysis.
Jialun Yang (Thu,) studied this question.
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