Fungrim entry: 21d9a0

\left\{ W_{-1}\!\left(z\right) : z \in \mathbb{C} \setminus \left\{0\right\} \right\} = \left(-\infty, -1\right] \cup \left\{ x + y i : x \in \mathbb{R} \;\mathbin{\operatorname{and}}\; y \in \mathbb{R} \;\mathbin{\operatorname{and}}\; \left(\left(0 < u < 2 \;\mathbin{\operatorname{and}}\; t \le v\right) \;\mathbin{\operatorname{or}}\; \left(1 \le u \le 2\right) \;\mathbin{\operatorname{or}}\; \left(1 < u < 3 \;\mathbin{\operatorname{and}}\; t > v\right)\right)\; \text{ where } t = x \operatorname{sinc}(y),\;v = -\cos(y),\;u = -\frac{y}{\pi} \right\}

TeX:

\left\{ W_{-1}\!\left(z\right) : z \in \mathbb{C} \setminus \left\{0\right\} \right\} = \left(-\infty, -1\right] \cup \left\{ x + y i : x \in \mathbb{R} \;\mathbin{\operatorname{and}}\; y \in \mathbb{R} \;\mathbin{\operatorname{and}}\; \left(\left(0 < u < 2 \;\mathbin{\operatorname{and}}\; t \le v\right) \;\mathbin{\operatorname{or}}\; \left(1 \le u \le 2\right) \;\mathbin{\operatorname{or}}\; \left(1 < u < 3 \;\mathbin{\operatorname{and}}\; t > v\right)\right)\; \text{ where } t = x \operatorname{sinc}(y),\;v = -\cos(y),\;u = -\frac{y}{\pi} \right\}

Definitions:

Fungrim symbol	Notation	Short description
`LambertW`	$W\!\left(z\right)$	Lambert W-function
`CC`	$\mathbb{C}$	Complex numbers
`OpenClosedInterval`	$\left(a, b\right]$	Open-closed interval
`Infinity`	$\infty$	Positive infinity
`ConstI`	$i$	Imaginary unit
`RR`	$\mathbb{R}$	Real numbers
`Sinc`	$\operatorname{sinc}(z)$	Sinc function
`Cos`	$\cos(z)$	Cosine
`Pi`	$\pi$	The constant pi (3.14...)

Source code for this entry:

Entry(ID("21d9a0"),
    Formula(Equal(Set(LambertW(z, -1), ForElement(z, SetMinus(CC, Set(0)))), Union(OpenClosedInterval(Neg(Infinity), -1), Set(Add(x, Mul(y, ConstI)), For(Tuple(x, y)), Where(And(Element(x, RR), Element(y, RR), Or(And(Less(0, u, 2), LessEqual(t, v)), Parentheses(LessEqual(1, u, 2)), And(Less(1, u, 3), Greater(t, v)))), Equal(t, Mul(x, Sinc(y))), Equal(v, Neg(Cos(y))), Equal(u, Neg(Div(y, Pi)))))))))

Topics using this entry

Lambert W-function