derivative of limit v. limit of derivative

richardt

Junior Member
Joined
Aug 27, 2013
Messages
56
Greetings:

Is it necessarily true that the derivative of a limit is equal to the "appropriate" limit of the derivative? More specifically, I am trying to prove d/dx ex = ex as follows: It is readily shown that limit(n-->inf)[1+x/n]n = ex. Hence if my opening suggestion is true, then d/dx ex = limit[d/dx [1+x/n]n] = limit[1+x/n]n-1
= limit(n-->inf)[1+x/n]n / limit(n-->inf)[1+x/n]1 = ex/1 = ex.

i) Is the derivative of limit indeed equal to the limit of derivative?

ii) Are there suggestions as to how to prove i)? Please, suggest only; I'd like to put it all together on my own.

Thank you kindly.

Rich
 
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