# Homework Help: Need a little help with a derivative problem please

1. Oct 9, 2009

If f(x) = 7sin(3 x) * (arcsin(x)), find f'( x ).

I'm assuming I need to use the product rule, but I am failing to set it up right. I assume it's with the beginning part and I'm just goofing up on what to do with the coefficient.

I think it's ((7sin3x)' * arcsinx) + (7sin(3x) + 1/(sqrt(1-x^2)).

If that's correct I'm just failing to get the derivative. I can't seem to remember how I should proceed with something in that form. I should be past this but I'm having trouble seeing it. Any help would be great.

Thank you

2. Oct 9, 2009

### LCKurtz

Your last + should be multiplication.

3. Oct 9, 2009

Ah yes it is I just typed it up wrong in my initial post. I cant seem to figure out the derivative though. The derivative of 7sin3x is not working out for me. I tried things like 7cos3x(3) but that doesnt seem to work. Any help would be great thanks

4. Oct 9, 2009

### Dick

I don't see anything wrong with 21*cos(3x) as the derivative of 7*sin(3x).

5. Oct 9, 2009

so would the final answer be

21cos3x(arcsinx)+(7sin3x)/(sqrt(1-x^2))

because that does not seem to be the right answer on my web assignment i dunno

6. Oct 9, 2009

### Dick

I can't really speak for web assignment, but it looks ok to me.

7. Oct 9, 2009