todo
x(t)=∑ni=1xi(t)ei(t)
∂∂tx(t)=∑ni=1((∂∂txi(t))ei(t)+xi(t)∂∂tei(t))
https://en.wikipedia.org/wiki/Fictitious_force
Wikipedia: https://en.wikipedia.org/wiki/Fictitious_force
Fréchet derivative