# Homework Help: Max and min problem with 3 unknowns

1. Jan 20, 2010

### Simon.T

Hi,

I have this question for a college assignment. It involves 3 'unknowns' (not 3 variables, since 2 are constants). The main difficulty I am having is inexperience with max and min problems where you cannot fully evalaute the solution.

I think I have made a reasonable attempt at a solution, I would appreciate it if someone would take a brief look tell me what you think.

Thanks!

1. The problem statement, all variables and given/known data

Find V for maximum E, hence find E_max.

u and $$\theta$$ are constants.

2. Relevant equations

Product rule: $$\frac{dy}{dx}=u\frac{dv}{dx}+v\frac{du}{dx}$$

3. The attempt at a solution

Last edited: Jan 21, 2010
2. Jan 20, 2010

### Staff: Mentor

Looks fine to me (although I just skimmed some of the algebra). Do you know yet if it's the correct answer?

3. Jan 20, 2010

### Simon.T

Hi, thanks for taking a look at my question.

The whole assignment isn't due for a week or so yet, so I won't find out for a while.

I am somewhat confident of my approach but was just wanting someone to look it over.

Cheers!