Formula:KLS:01.14:05

<< Formula:KLS:01.14:04

formula in Some q-analogues of special functions

Formula:KLS:01.14:06 >>

${\displaystyle{\displaystyle{\displaystyle\mathrm{cos}_{q}\!\left(z\right):=\frac{\mathrm{e}_{q}\!\left(\mathrm{i}z)+{\mathrm{e}}_{q}(-\mathrm{i}z\right)}{2}=\sum_{n=0}^{\infty}\frac{(-1)^{n}z^{2n}}{\left(q;q\right)_{2n}}}}}$

Proof

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Symbols List

${\displaystyle{\displaystyle{\displaystyle\mathrm{cos}_{q}}}}$ : ${\displaystyle{\displaystyle{\displaystyle q}}}$-analogue of the cosine function ${\displaystyle{\displaystyle{\displaystyle\cos_{q}}}}$ used in KLS : http://drmf.wmflabs.org/wiki/Definition:qcosKLS
${\displaystyle{\displaystyle{\displaystyle\mathrm{e}_{q}}}}$ : ${\displaystyle{\displaystyle{\displaystyle q}}}$-analogue of the exponential function ${\displaystyle{\displaystyle{\displaystyle\mathrm{e}_{q}}}}$ used in KLS : http://drmf.wmflabs.org/wiki/Definition:qexpKLS
${\displaystyle{\displaystyle{\displaystyle\mathrm{i}}}}$ : imaginary unit : http://dlmf.nist.gov/1.9.i
${\displaystyle{\displaystyle{\displaystyle\Sigma}}}$ : sum : http://drmf.wmflabs.org/wiki/Definition:sum
${\displaystyle{\displaystyle{\displaystyle(a;q)_{n}}}}$ : ${\displaystyle{\displaystyle{\displaystyle q}}}$-Pochhammer symbol : http://dlmf.nist.gov/5.18#i http://dlmf.nist.gov/17.2#SS1.p1

Bibliography

Equation in Section 1.14 of KLS.

URL links

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<< Formula:KLS:01.14:04

formula in Some q-analogues of special functions

Formula:KLS:01.14:06 >>