Leonhard Euler · 1748 · Internet Archive
Introductio in analysin infinitorum
All 320 leaves · leaf 193
Transcription
FRACTARUM EVOLUTIONE.
165
$\frac{1+z+zz}{1+z^4}$, cujus denominator $1+z^4$ cum habeat Factores $1+z\sqrt{2}+zz$ & $1-z\sqrt{2}+zz$, resolutio denuo suscipi potest; fit autem $\Phi = \frac{\pi}{4}$ & priori casu $f = -1$ posteriori $f = +1$.
CAP.
XII.
EXEMPLUM. II.
Sit igitur proposita hæc fractio resolvenda
$\frac{1+z+zz}{(1+z\sqrt{2}+zz)(1-z\sqrt{2}+zz)}$
& erit $M = 1+z+zz$; & pro priore Factore habebitur $f = -1$; $\Phi = \frac{\pi}{4}$, & $Z = 1-z\sqrt{2}+zz$, unde erit
$P = 1 - \cos.\frac{\pi}{4} + \cos.\frac{2\pi}{4} = \frac{\sqrt{2}-1}{\sqrt{2}}$
$P = - \sin.\frac{\pi}{4} + \sin.\frac{2\pi}{4} = \frac{\sqrt{2}-1}{\sqrt{2}}$
$Q = 1 + \sqrt{2}.\cos.\frac{\pi}{4} + \cos.\frac
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