"Surely You're Joking, Mr. Feynman!", p72:
That book [Woods`Advanced Calculus]
also showed how to
differentiate parameters under the integral sign
--it's a certain operation. It turns out
that's not taught very much in the universities;
they don't emphasize it.
But I caught on how to use that method,
and I used that one damn tool again and again.
So because I was self-taught using that book,
I had peculiar methods of doing integrals.
wolfram` Leibniz Integral Rule
[ tagged as Recreational Mathematics >
Mathematics in the Arts > Mathematics in Literature >
Surely You're Joking, Mr. Feynman! ]
Leibniz integral rule gives a formula foralso known as:
differentiation of a definite integral whose limits are
functions of the differential variable,
It is sometimes known as
differentiation under the integral sign.
differentiating under the integral sign,. see thorough review of related theorems;
differentiation with respect to a parameter,
or sometimes even Feynman Integration.
see Goldmakher's applications of it .