1. Mar 16, 2007

### kasse

"You are standing at the point (30, 20, 5) on a hill with the shape of the surface z=100exp((-x^2+3y^2)/701). In what direction should you proceed in order to climb most steeply?"

SInce the grad vector allegedly points in the most steep direction of the surface, I guess I'll have to compute that one. But I'm not sure if I'm suppoesd to compute the partials of all of x, y and z or only x and y in the gradient. How can I know that?

2. Mar 16, 2007

### neutrino

Edit: z is a function of x and y.

3. Mar 16, 2007

### tim_lou

the thing is, it depends on what kind of increase you want. obviously from the question, it implies the direction that z ("climb most steeply") increases most rapidly. so, take the derivatives with respect to z.

4. Mar 17, 2007

### HallsofIvy

No, it doesn't. You are given that z is a function of x and y so take the gradient of z using the partial derivatives of z with respcect to x and y. (That may be what tim lou meant to say.)

It would make no sense to talk about taking partial derivatives of x and y- with respect to what other variables?

Why "allegedly"? And you surely, by "that one" mean the gradient of z don't you? So why was there any question?