# How to solve this:f(x)=(x^2) (ln x) (cos x)

1. Jan 21, 2006

### teng125

does anybody knows how to solve this:f(x)=(x^2) (ln x) (cos x) ??

i would like to know the final answer is it = exp (2/x + 1/x ln x - tan x)??

2. Jan 21, 2006

### HallsofIvy

We can't tell you the answer if you won't tell us the question! I don't know what you mean by "solve f(x)= ". Since you titled this "derivatives" I might guess you mean "find the derivative of f(x)" but in that case your "answer" makes no sense at all. I can only guess that you means something else entirely.

Please state the question clearly and don't just show an answer, show us how you got it.

3. Jan 21, 2006

### teng125

ya,that's the question....myanswer it wrong.May i know how to do it??

4. Jan 21, 2006

### HallsofIvy

I'll repeat:Please state the question clearly and don't just show an answer, show us how you got it.

I really doubt that you have a homework problem that says, word for word, "solve f(x)=(x^2) (ln x) (cos x)". It makes no sense to say "solve" a function.

Now, how did you attempt to do this problem?

5. Jan 21, 2006

### gaganpreetsingh

Do you know that d(uv)/dx = v(du/dx) + u(dv/dx)
Now here you have three functions. Can you take two functions as one and then apply the above rule again i.e. apply it two times.

6. Jan 21, 2006

### Ouabache

Have they move teaching about derivatives, to precalculus courses?