Fungrim entry: 931d89

\left|\Gamma(z)\right| \ge {\left(2 \pi\right)}^{1 / 2} \left|{z}^{z - 1 / 2} {e}^{-z}\right| \exp\!\left(-\frac{1}{6 \left|z\right|}\right)

Assumptions:

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

TeX:

\left|\Gamma(z)\right| \ge {\left(2 \pi\right)}^{1 / 2} \left|{z}^{z - 1 / 2} {e}^{-z}\right| \exp\!\left(-\frac{1}{6 \left|z\right|}\right)

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

Definitions:

Fungrim symbol	Notation	Short description
`Abs`	$\left\|z\right\|$	Absolute value
`Gamma`	$\Gamma(z)$	Gamma function
`Pow`	${a}^{b}$	Power
`Pi`	$\pi$	The constant pi (3.14...)
`Exp`	${e}^{z}$	Exponential function
`CC`	$\mathbb{C}$	Complex numbers
`Re`	$\operatorname{Re}(z)$	Real part

Source code for this entry:

Entry(ID("931d89"),
    Formula(GreaterEqual(Abs(Gamma(z)), Mul(Mul(Pow(Mul(2, Pi), Div(1, 2)), Abs(Mul(Pow(z, Sub(z, Div(1, 2))), Exp(Neg(z))))), Exp(Neg(Div(1, Mul(6, Abs(z)))))))),
    Variables(z),
    Assumptions(And(Element(z, CC), GreaterEqual(Re(z), 0), NotEqual(z, 0))))

Topics using this entry

Bounds and inequalities for the gamma function