ピコーンの等式
{\displaystyle {\begin{aligned}&\left({\frac {u}{v}}(p_{1}u'v-p_{2}uv')\right)'\\&\quad =\left(up_{1}u'-p_{2}v'u^{2}{\frac {1}{v}}\right)'\\&\quad =u'p_{1}u'+u(p_{1}u')'-(p_{2}v')'u^{2}{\frac {1}{v}}-p_{2}v'2uu'{\frac {1}{v}}+p_{2}v'u^{2}{\frac {v'}{v^{2}}}\\&\quad =p_{1}u'^{2}-2p_{2}{\frac {uu'v'}{v}}+p_{2}{\frac {u^{2}v'^{2}}{v^{2}}}+u(p_{1}u')'-(p_{2}v')'{\frac {u^{2}}{v}}\\&\quad =p_{1}u'^{2}-p_{2}u'^{2}+p_{2}u'^{2}-2p_{2}u'{\frac {uv'}{v}}+p_{2}\left({\frac {uv'}{v}}\right)^{2}-u(q_{1}u)+(q_{2}v){\frac {u^{2}}{v}}\\&\quad =\left(p_{1}-p_{2}\right)u'^{2}+p_{2}\left(u'-v'{\frac {u}{v}}\right)^{2}+\left(q_{2}-q_{1}\right)u^{2}.\end{aligned}}}