Leonhard Euler · 1748 · Internet Archive
Introductio in analysin infinitorum
All 320 leaves · leaf 61
Transcription
FUNCTIONUM.
33
tes $A, B, C, D,$ &c. invenientur omnes fractiones partiales, CAP. II. quæ ex denominatoris $N$ Factore $(p-qz)^n$ nascuntur.
EXEMPLUM.
Sit proposita ista Functio fracta $\frac{1+zz}{z^5(1+z^3)}$ ex cujus denominatoris Factore $z^5$ nascantur hæ fractiones partiales $\frac{A}{z^5} + \frac{B}{z^4} + \frac{C}{z^3} + \frac{D}{z^2} + \frac{E}{z}$. Ad quarum numeratores constantes inveniendos, erit $M=1+zz$ atque $Z=1+z^3$; & $\frac{p}{q}=0$. Sequens ergo calculus ineatur.
Primum est $A = \frac{M}{Z} = \frac{1+zz}{1+z^3}$, posito $z=0$; ergo $A=1$.
Ponatur $P = \frac{M-AZ}{z} = \frac{zz-z^3}{z} = z-zz$. Eritque secundo $B = \frac{P}{Z} = \frac{z-zz}{1+z^3}$, posito $z=0$; ergo $B=0$.
Ponatur $Q = \frac{P-BZ}{z} = \frac{z-zz}{z} = 1-z$; eritque tertio $C = \frac{Q}{Z} = \frac{1-z}{1+z^3}$, posito $z=0$: ergo $C=1$.
Ponatur $R = \frac{Q-CZ}{z} = \frac{-z-z^3}{z} = -1-zz$; erit quarto $D = \frac{R}{Z} = \frac{-1-zz}{1+z^3}$, posito $z=0$; ex quo fit $D=-1$.
Ponatur $S = \frac{R-DZ}{z} = \frac{-zz+z^3}{z} = -z+zz$; erit quinto $E = \frac{S}{Z} = \frac{-z+zz}{1+z^3}$, posito $z=0$; unde fit $E=0$.
Quo circa fractiones partiales quæsitæ erunt hæ:
$\frac{1}{z^5} + \frac{0}{z^4} + \frac{1}{z^3} - \frac{1}{z^2} + \frac{0}{z}$.
Euleri *Introduct. in Anal. infin. parv.* E 46. *Quæ-*
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