Fungrim entry: f946a5

\psi\!\left(z\right) = -\gamma + \int_{0}^{\infty} \frac{{e}^{-t} - {e}^{-z t}}{1 - {e}^{-t}} \, dt

Assumptions:

z \in \mathbb{C} \;\mathbin{\operatorname{and}}\; \operatorname{Re}(z) > 0

TeX:

\psi\!\left(z\right) = -\gamma + \int_{0}^{\infty} \frac{{e}^{-t} - {e}^{-z t}}{1 - {e}^{-t}} \, dt

z \in \mathbb{C} \;\mathbin{\operatorname{and}}\; \operatorname{Re}(z) > 0

Definitions:

Fungrim symbol	Notation	Short description
`DigammaFunction`	$\psi\!\left(z\right)$	Digamma function
`ConstGamma`	$\gamma$	The constant gamma (0.577...)
`Integral`	$\int_{a}^{b} f(x) \, dx$	Integral
`Exp`	${e}^{z}$	Exponential function
`Infinity`	$\infty$	Positive infinity
`CC`	$\mathbb{C}$	Complex numbers
`Re`	$\operatorname{Re}(z)$	Real part

Source code for this entry:

Entry(ID("f946a5"),
    Formula(Equal(DigammaFunction(z), Add(Neg(ConstGamma), Integral(Div(Sub(Exp(Neg(t)), Exp(Neg(Mul(z, t)))), Sub(1, Exp(Neg(t)))), For(t, 0, Infinity))))),
    Variables(z),
    Assumptions(And(Element(z, CC), Greater(Re(z), 0))))

Topics using this entry

Digamma function