# Partial derivative of a function of several variables with an element of a matrix on its definition

Ricardo Halla II shared this question 5 years ago

Hello

In my problem I have a matrix M, a several variables function f(u,v) that depends on an element of the matrix M and the partial derivative of f(u,v) with respect to the variable u. I called this partial derivative fu(u,v). You can see this in the attach1.

The problem is that the value of fu(u,v) depends on a term M(1,0), as you can see in the attach2. The term M(1,0) is undefined because we don't have the column number 0, so the entire function fu(u,v) is undefined. But we know that the real value of fu(u,v) in this case is 6*u.

So, I have this kind of problem derivating a function of several variables that has an element of a matrix on its definition. The same happens using version 5 and 6 of Geogebra.

Can someone help me?

My Geogebra is in Portuguese, so:

Função de várias variáveis = Function of several variables

Elemento = Element

al definir f(u,v) usando M(row,column) se ve que GG entiende que M es una funcion tambien y así deriva el numero de columna haciendolo cero

si escribes en la forma standar deberías definir f escribiendo 2y^2+element(M,2,1) x^2 (u,v son standar para surface y t para rectas). luego puedes derivar respecto x y usar f o f' con cualquier valor

también podrias definir k=element(M,2,1) y usar k en la definicion de la funcion

1

1

Here it is.

2

al definir f(u,v) usando M(row,column) se ve que GG entiende que M es una funcion tambien y así deriva el numero de columna haciendolo cero

si escribes en la forma standar deberías definir f escribiendo 2y^2+element(M,2,1) x^2 (u,v son standar para surface y t para rectas). luego puedes derivar respecto x y usar f o f' con cualquier valor

también podrias definir k=element(M,2,1) y usar k en la definicion de la funcion

1

Thank you!

Defining "k = element(M,2,1)" and using "k" in the definition of the function worked.