Delta vs. Differential
I'm reading an old (1963) ordinary differential equations textbook. As a prelude to the section on separable DEs, there is a section explaining what a differential is. It says that, if y is a function of x (y=f(x)), then the differential dy is:
dy = f'(x)Δx
Why Δx and not dx? There is mention of the fact that writing dx instead became customary over time, but no explanation as to why it wasn't that way in the first place.
dy = f'(x)Δx
Why Δx and not dx? There is mention of the fact that writing dx instead became customary over time, but no explanation as to why it wasn't that way in the first place.