ELLIPTIC INTEGRALS AND SOME APPLICATIONS Jay Villanueva Florida Memorial University 15800 NW 42nd Ave Miami, FL 33054
[email protected] 1. Introduction 1.1 How they arose – perimeter of an ellipse 1.2 Standard forms from Legendre, Jacobi, and Landen 2. Properties and examples 2.1 Evaluating integrals 2.2 Elliptic functions 3. Applications 3.1 Calculus 3.1.1 Perimeter of an ellipse 3.1.2 Arclength of a lemniscate 3.2 Physics 3.2.1 Finite-amplitude pendulum 3.2.2 Perihelion of Mercury 4. Conclusion References: 1. JW Armitage and WF Eberlein, 2006. Elliptic Functions. Cambridge University Press. 2. HM Kean and V Moll, 1997. Elliptic Curves. Cambridge University Press. 3. DF Lawden, 1989. Elliptic Functions and Applications. New York: Springer Verlag. 4. V Prasolov and Y Sovolyev, 1997. Elliptic Functions and Elliptic Integrals. Providence, RI: American Mathematical Society. 5. HE Rauch and A Lebowitz, 1973. Elliptic Functions, Theta Functions, and Riemann Surfaces. MD: Williams and Wilkins Co. 6. Schaum’s Outlines, 1996. Advanced Calculus. NY: McGraw-Hill. Elliptic integrals arose from the attempts to find the perimeter of an ellipse: 푥2 푦2 + = 1, 푥 = 푎 cos 휃, 푦 = 푏 sin 휃 푎2 푏2 푎 2휋 퐿 = 푑푠 = 2 √1 + 푦′2푑푥 = 1 + 푏2푐표푠2휃(−푎푠푛휃)푑휃, ∫ ∫−푎 ∫0 √ which last integral cannot be evaluated by elementary functions, viz., trigonometric, exponential, or logarithmic functions. The incomplete elliptic integral of the first kind is defined as 휙 푑휃 푢 = 퐹(푘, 휙) = ∫ , 0 < 푘 < 1, 0 √1−푘2푠푛2휃 where 휙 is the amplitude of 퐹(푘, 휙) or u, written 휙 = am 푢, and k is the modulus, 푘 = mod 푢.