Formule de Petry
\(e=100 \times m \times \dfrac{k}{a^2} \times \log\! \left[1+\dfrac{1}{2} \left(\dfrac{v}{100} \right)^2 \right] \)
\(e=100 \times m \times \dfrac{k}{a^2} \times \log\! \left[1+\dfrac{1}{2} \left(\dfrac{v}{100} \right)^2 \right] \)