@Shubham Dhull
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I think there is no closed form for \(\dfrac d{dx}x!\), that is why we use digamma function.
–
Chew-Seong Cheong
·
8 months, 3 weeks ago

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@Chew-Seong Cheong
–
okay... i was thinking why there was a need of new function just to define d/dx of gamma function. now i understand it !
–
Shubham Dhull
·
8 months, 3 weeks ago

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@Shubham Dhull
–
I actually used Wolfram Alpha to check \(\dfrac d{dx}x!\), it gave the same result involving \(\psi(x)\). Check here.
–
Chew-Seong Cheong
·
8 months, 3 weeks ago

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@Shubham Dhull
–
\( \text{ Gamma function is not in the syllabus of IIT Advanced } \\ \text{ The function is defined as } \Gamma{(1+x)}=\displaystyle \int_{0}^{\infty} e^{-t}t^{x} dt \\ \text{For integer values of x the value of integral is } \Gamma{(1+x)}=x! \)
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Sambhrant Sachan
·
8 months, 3 weeks ago

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@Sambhrant Sachan
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The motivation of the invention by Euler of \(\Gamma (z)\) is to extend factorial beyond the integers. It connects the integer factorials in a smooth curve.
–
Chew-Seong Cheong
·
8 months, 3 weeks ago

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@Sambhrant Sachan
–
yes you are right * but * some questions can be easily solved using gamma and beta functions also i did'nt knew the thing i asked was related to gamma or digamma function , i asked purely out of curiosity as i thought of it in my leisure time.
–
Shubham Dhull
·
8 months, 3 weeks ago

## Comments

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TopNewestGamma function \(\Gamma (1+x) = x!\). \(\implies \dfrac d{dx}x! = \dfrac d{dx} \Gamma (1+x) = \Gamma' (1+x) \). As digamma function is defined as: \(\psi (z) = \dfrac d{dz} \ln \Gamma (z) = \dfrac {\Gamma' (z)}{\Gamma (z)} \). \(\implies \dfrac d{dx}x! = \Gamma' (1+x) = \Gamma (1+x) \psi (1+x)\). – Chew-Seong Cheong · 8 months, 3 weeks ago

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– Shubham Dhull · 8 months, 3 weeks ago

okay thanks sirLog in to reply

– Chew-Seong Cheong · 8 months, 3 weeks ago

I think there is no closed form for \(\dfrac d{dx}x!\), that is why we use digamma function.Log in to reply

– Shubham Dhull · 8 months, 3 weeks ago

okay... i was thinking why there was a need of new function just to define d/dx of gamma function. now i understand it !Log in to reply

here. – Chew-Seong Cheong · 8 months, 3 weeks ago

I actually used Wolfram Alpha to check \(\dfrac d{dx}x!\), it gave the same result involving \(\psi(x)\). CheckLog in to reply

– Sambhrant Sachan · 8 months, 3 weeks ago

\( \text{ Gamma function is not in the syllabus of IIT Advanced } \\ \text{ The function is defined as } \Gamma{(1+x)}=\displaystyle \int_{0}^{\infty} e^{-t}t^{x} dt \\ \text{For integer values of x the value of integral is } \Gamma{(1+x)}=x! \)Log in to reply

– Chew-Seong Cheong · 8 months, 3 weeks ago

The motivation of the invention by Euler of \(\Gamma (z)\) is to extend factorial beyond the integers. It connects the integer factorials in a smooth curve.Log in to reply

– Shubham Dhull · 8 months, 3 weeks ago

yes you are right * but * some questions can be easily solved using gamma and beta functions also i did'nt knew the thing i asked was related to gamma or digamma function , i asked purely out of curiosity as i thought of it in my leisure time.Log in to reply

Thanks @Chew-Seong Cheong and @Sambhrant Sachan for stopping by and helping me with my problem , plz keep supporting. – Shubham Dhull · 8 months, 3 weeks ago

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