Hello my question was about higher order partial derivatives questions, basically what got me thinking was let's say for example a function is defined by two variables say, f(x,y), when we take second order partial derivative with respect to x each time wouldn't we get the second order partial derivative to be 0.

because when i was learning in class this is what i understood that a partial derivative was basically calcualtion of the tangent line at a point on the surface of a given a function parallel to which ever axis your doing the derivation with respect to.

Isnt the partial derivative the first time a constant and than the second time you take the partial derivative 0?