Author Topic: section 2.1  (Read 211 times)

Arush Mitra

  • Newbie
  • *
  • Posts: 1
  • Karma: 0
    • View Profile
section 2.1
« on: September 21, 2016, 01:59:17 PM »
could someone please explain how do we get from equation 1 to equation 2. please check the attached file to view the equations.
thanks in advance

Victor Ivrii

  • Administrator
  • Elder Member
  • *****
  • Posts: 1332
  • Karma: 0
    • View Profile
    • Personal website of Victor Ivrii
Re: section 2.1
« Reply #1 on: September 21, 2016, 04:55:42 PM »
No, we do not get equation (2) from (1) but we observe that if (1) holds and we take $dx$, $dt$ satisfying (1) then
\begin{equation}
du=u_tdt +u_xdx= (u_t a + u_xb)\frac{dt}{a}=0.
\end{equation}