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Paradoxical Euler: Integrating by Differentiating

Published online by Cambridge University Press:  23 January 2015

Andrew Fabian
Affiliation:
Department of Mathematics, Rowan University, Glassboro, NJ 08028 USA, e-mails:[email protected]; [email protected]
Hieu D. Nguyen
Affiliation:
Department of Mathematics, Rowan University, Glassboro, NJ 08028 USA, e-mails:[email protected]; [email protected]

Extract

Every student of calculus learns that one typically solves a differential equation by integrating it. However, as Euler showed in his 1758 paper (E236), Exposition de quelques paradoxes dans le calcul intégral (Explanation of certain paradoxes in integral calculus) [1], there are differential equations that can be solved by actually differentiating them again. This initially seems paradoxical or, as Euler describes it in the introduction of his paper:

Here I intend to explain a paradox in integral calculus that will seem rather strange: this is that we sometimes encounter differential equations in which it would seem very difficult to find the integrals by the rules of integral calculus yet are still easily found. not by the method of integration. but rather in differentiating the proposed equation again; so in these cases, a repeated differentiation leads us to the sought integral.

Type
Articles
Copyright
Copyright © The Mathematical Association 2013

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References

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