Dear all,(adsbygoogle = window.adsbygoogle || []).push({});

I have a confusion about partial derivatives.

Say I have a function as

[itex]y=f(x,t)[/itex]

and we know that

[itex]x=g(t)[/itex]

1. Does it make sense to talk about partial derivatives like [itex]\frac{\partial y}{\partial x}[/itex] and [itex]\frac{\partial y}{\partial t}[/itex] ?

I doubt, because the definition of partial derivative is the change in the function due to the change on the selected variable ( other variables are kept constant).

2. If it does not make sense, then how in Eulerâ€“Lagrange equation we use the partial derivatives with respect to a function(x(t)) and its derivative(x'(t)) while they depend on one another.

Your help would be appreciated.

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

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!

# Confusion about partial derivatives

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