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Question Number 17634 by tawa tawa last updated on 08/Jul/17

y = x!  ,     Find   y′

$$\mathrm{y}\:=\:\mathrm{x}!\:\:,\:\:\:\:\:\mathrm{Find}\:\:\:\mathrm{y}' \\ $$

Answered by alex041103 last updated on 09/Jul/17

Because x! is defined only for non−negative  integers, i.e. the function isn′t continious  we cannot intagrate or diferentiate it.  There is ananalitic continuation  of  the factorial function called the  Gamma function  x!=Γ(x+1)=∫_(  0) ^∞ t^x e^(−t) dt  You can search for the derivitive of  the gamma function.

$${Because}\:{x}!\:{is}\:{defined}\:{only}\:{for}\:{non}−{negative} \\ $$$${integers},\:{i}.{e}.\:{the}\:{function}\:{isn}'{t}\:{continious} \\ $$$${we}\:{cannot}\:{intagrate}\:{or}\:{diferentiate}\:{it}. \\ $$$${There}\:{is}\:{ananalitic}\:{continuation} \\ $$$${of}\:\:{the}\:{factorial}\:{function}\:{called}\:{the} \\ $$$${Gamma}\:{function} \\ $$$${x}!=\Gamma\left({x}+\mathrm{1}\right)=\underset{\:\:\mathrm{0}} {\overset{\infty} {\int}}{t}^{{x}} {e}^{−{t}} {dt} \\ $$$${You}\:{can}\:{search}\:{for}\:{the}\:{derivitive}\:{of} \\ $$$${the}\:{gamma}\:{function}. \\ $$

Commented by tawa tawa last updated on 09/Jul/17

God bless you sir.

$$\mathrm{God}\:\mathrm{bless}\:\mathrm{you}\:\mathrm{sir}. \\ $$

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