- #1
Tony Hau
- 101
- 30
So in my lecture notes on Differential Equations, it states that a first order ODE is exact if A(x,y)dx + B(x,y)dy = 0 and ∂A/∂y = ∂B/∂x. Okay I accept this definition.
Then, there is a sentence like this:
Our goal is to find the function V(x,y) satisfying
Adx + Bdy = dV = ∂V/∂x(dx) + ∂V/∂y(dy), where A(x,y) =∂V/∂x and B(x,y) =∂V/∂y.
I am confused here. Why dV = ∂V/∂x(dx) + ∂V/∂y(dy)? I think you can say that dx cancels with ∂x and dy cancels with ∂y and so it is the total change in infinitesimal V in both x and y direction. Is my concept correct? I am okay with the idea that dx cancels with dx but still, I am not really convinced that dx cancels with ∂x.
Then, there is a sentence like this:
Our goal is to find the function V(x,y) satisfying
Adx + Bdy = dV = ∂V/∂x(dx) + ∂V/∂y(dy), where A(x,y) =∂V/∂x and B(x,y) =∂V/∂y.
I am confused here. Why dV = ∂V/∂x(dx) + ∂V/∂y(dy)? I think you can say that dx cancels with ∂x and dy cancels with ∂y and so it is the total change in infinitesimal V in both x and y direction. Is my concept correct? I am okay with the idea that dx cancels with dx but still, I am not really convinced that dx cancels with ∂x.