# Math Help - Function of two variables

1. ## Function of two variables

I am given that we are to let F(u,v) be a function of two variables. I am asked to find f' (x)
for;

f(x) = F(x,3) and f(x) = F(x,x)

I have not a single idea on what I am suppose to do. Can someone tell me? Thanks!

2. Originally Posted by Frostking
I am given that we are to let F(u,v) be a function of two variables. I am asked to find f' (x)
for;

f(x) = F(x,3) and f(x) = F(x,x)

I have not a single idea on what I am suppose to do. Can someone tell me? Thanks!
In the first one it $f' = F_u(x,3)$, (you just substituted in for v), the second $f' = F_u(x,x) + F_v(x,x)$.

Here's an example. Consider the function

$F(u,v) = u^3 \sin v$ so $f = x^3 \sin x$ and $f' = \underbrace{3 x^2 \sin x}_{F_u(x,x)} + \underbrace{x^3 \cos x}_{F_v(x,x)}$