dit plus haut),
![{\displaystyle \lambda =f\Pi +g\Psi +h\Phi ,\quad \lambda =f'\Pi +g'\Psi +h'\Phi ,\quad \nu =f''\Pi +g''\Psi +h''\Phi .}](https://wikimedia.org/api/rest_v1/media/math/render/svg/01af636ceb5ad581997ca725334d53c02f929466)
De plus, si dans les expressions de
trouvées au commencement de cette Remarque, on substitue pour
![{\displaystyle \mathrm {\frac {GH+FL}{\Delta }} ,\quad \mathrm {\frac {LN-G^{2}}{\Delta }} ,\ldots }](https://wikimedia.org/api/rest_v1/media/math/render/svg/64f7b3a8fb6ea52a42bc5d657a9971fe2362f2f8)
leurs valeurs
![{\displaystyle \alpha ff'+\beta gg'+\gamma hh',\quad \alpha f'^{2}+\beta g'^{2}+\gamma h'^{2},\ldots ,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/c13ffc1b4922f895f44518f1a1fbe4b2d3ecc2dc)
et qu’on y introduise les quantités
on trouvera
![{\displaystyle {\begin{aligned}{\frac {d\varpi }{dt}}=&\alpha f\ \ \Pi +\beta g\ \ \Psi +\gamma h\ \,\Phi ,\\{\frac {d\varphi }{dt}}=&\alpha f'\ \Pi +\beta g'\ \Psi +\gamma h'\ \Phi ,\\{\frac {d\psi }{dt}}=&\alpha f''\Pi +\beta g''\Psi +\gamma h''\Phi .\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e59d6f57f574ebe5738511d3b35b0d03bf534574)
De là on aura, après les substitutions,
![{\displaystyle {\begin{aligned}\nu {\frac {d\varphi }{dt}}-\mu {\frac {d\psi }{dt}}=&(\alpha -\beta )(g''f'-g'f'')\Pi \Psi \\+&(\gamma -\alpha )(f''h'-f'h'')\Pi \Phi \\+&(\beta -\gamma )(h''g'\ -h'g'')\Psi \Phi \,;\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/a6174edc789a9506bee0325360e55fdffaa27290)
c’est-à-dire par les formules du no 7
![{\displaystyle \nu {\frac {d\varphi }{dt}}-\mu {\frac {d\psi }{dt}}=(\alpha -\beta )h\Pi \Psi +(\gamma -\alpha )g\Pi \Phi +(\beta -\gamma )f\Psi \Phi \,;}](https://wikimedia.org/api/rest_v1/media/math/render/svg/9c01f7f8d3b4b71c7cd4f99c32b89a3e6bceb48f)
de sorte que l’équation (13) de la solution ci-dessus deviendra
![{\displaystyle {\frac {fd\Pi +gd\Psi +hd\Phi }{(\beta -\gamma )f\Psi \Phi +(\gamma -\alpha )g\Pi \Phi +(\alpha -\beta )h\Pi \Psi }}=dt.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/d4d74d39b8909b85bdfa3d45585c20074c53ac47)
Substituons au lieu de
et
leurs valeurs tirées des équations
![{\displaystyle \mathrm {\Pi ^{2}+\Psi ^{2}+\Phi ^{2}=k^{2},\quad \alpha \Pi ^{2}+\beta \Psi ^{2}+\gamma \Phi ^{2}=E^{2}} ,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/d9d952f86de226c187aed01625520212dcefe9e5)
lesquelles donnent
![{\displaystyle d\Psi ={\frac {(\gamma -\alpha )\Pi d\Pi }{(\beta -\gamma )\Psi }},\quad d\Phi ={\frac {(\alpha -\beta )\Pi d\Pi }{(\beta -\gamma )\Phi }},}](https://wikimedia.org/api/rest_v1/media/math/render/svg/318fd13fc99813b6fbd1f3e560900648cbb7079c)