Fungrim entry: d84519

\sum_{n=0}^{\infty} P_{n}\!\left(x\right) {z}^{n} = \frac{1}{\sqrt{1 - 2 x z + {z}^{2}}}

Assumptions:

x \in \left[-1, 1\right] \,\mathbin{\operatorname{and}}\, z \in \mathbb{C} \,\mathbin{\operatorname{and}}\, \left|z\right| \lt 1

TeX:

\sum_{n=0}^{\infty} P_{n}\!\left(x\right) {z}^{n} = \frac{1}{\sqrt{1 - 2 x z + {z}^{2}}}

x \in \left[-1, 1\right] \,\mathbin{\operatorname{and}}\, z \in \mathbb{C} \,\mathbin{\operatorname{and}}\, \left|z\right| \lt 1

Definitions:

Fungrim symbol	Notation	Short description
`LegendrePolynomial`	$P_{n}\!\left(z\right)$	Legendre polynomial
`Pow`	${a}^{b}$	Power
`Infinity`	$\infty$	Positive infinity
`Sqrt`	$\sqrt{z}$	Principal square root
`ClosedInterval`	$\left[a, b\right]$	Closed interval
`CC`	$\mathbb{C}$	Complex numbers
`Abs`	$\left\|z\right\|$	Absolute value

Source code for this entry:

Entry(ID("d84519"),
    Formula(Equal(Sum(Mul(LegendrePolynomial(n, x), Pow(z, n)), Tuple(n, 0, Infinity)), Div(1, Sqrt(Add(Sub(1, Mul(Mul(2, x), z)), Pow(z, 2)))))),
    Variables(x, z),
    Assumptions(And(Element(x, ClosedInterval(-1, 1)), Element(z, CC), Less(Abs(z), 1))))

Topics using this entry

Legendre polynomials