(adsbygoogle = window.adsbygoogle || []).push({}); A trick on PDE??

Hi all.

I am reading a text in mathematical wave theory.

I saw and am confused by a manipulation of a PDE, as shown in the attached figure.

I don't really undertand how the equation (1.9) is transformed by "introducing the charcteristic variables). (as indicated by the red arrow and the question mark)

I guess there are some missing steps? Could somone fill in the missing links so that I could know what's going on there.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# A trick on PDE?

**Physics Forums | Science Articles, Homework Help, Discussion**