Friday, 15 March 2013

calculus - Textbooks that use notation with explicit argument variable in the upper bound intx for "indefinite integrals."

I dare to ask a question similar to a closed one but more precise.



Are there any established textbooks or other serious published work that use x notation instead of for the so-called "indefinite integrals"?




(I believe I've seen it already somewhere, probably in the Internet, but I cannot find it now.)



So, I am looking for texts where the indefinite integral of cos would be written something like:
xcos(t)dt=sin(x)C
or
xcos(x)dx=sin(x)+C.




(This notation looks more sensible and consistent with the one for definite integrals than the common one with bare .)



Some context.



IMO, the indefinite integral of f on a given interval I of definition of f should not be defined as the set of antiderivatives of f on I but as the set of all functions F of the form
F(x)=xaf(t)dt+C,xI,
with aI and C a constant (or as a certain indefinite particular function of such form).

In other words, I think that indefinite integrals should be defined in terms of definite integrals and not in terms of antiderivatives.
(After all, the integral sign historically stood for a sum.)



In this case, the fact that the indefinite integral of a continuous function f on an interval I coincides with the set of antiderivatives of f on I is the contents of the first and the second fundamental theorems of calculus:




  1. the first fundamental theorem of calculus says that every representative of the indefinite integral of f on I is an antiderivative of f on I, and


  2. the second fundamental theorem of calculus says that every antiderivative of f on I is a representative of the indefinite integral of f on I (it is an easy corollary of the first one together with the mean value theorem).


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