Trig derv. problem

**FreaKariDunk** · February 26th 2011, 04:04 PM

Find F'(x)=x2(1 + cos(x))

Should I dist. the x^2?

I cannot seem to get started.
Thanks.

**e^(i*pi)** · February 26th 2011, 04:08 PM

Yes you can, then use the product rule on the second term: $F'(x) = x^2+x^2 \cos(x)$ . Or you can use the product rule directly with $u = x^2 \text{ and } v = 1+\cos(x)$ . You get the same result.

Out of interest are you trying to find the second derivative or is F'(x) a typo?

**FreaKariDunk** · February 26th 2011, 04:10 PM

I have a whole gaggle of things I have to do with this problem, and I've been putting it off. But i want to get it done to go to a baseball game(fella watch) tomorrow. Sigh. Responsibility. Would Substitution be easier or should I just buck up and do it?

**e^(i*pi)** · February 26th 2011, 04:14 PM

A sub won't help, you'd still have to do the product rule which really isn't that much trouble

**FreaKariDunk** · February 26th 2011, 04:18 PM

so: 2x+2xCos(x)-x^2Sin(x)?

**e^(i*pi)** · February 26th 2011, 05:21 PM

Originally Posted by FreaKariDunk

so: 2x+2xCos(x)-x^2Sin(x)?

Yes. You can also factor out x to give: $x(2-2\cos(x)-x\sin(x))$

**NOX Andrew** · February 26th 2011, 05:34 PM

Just in case FreaKariDunk reads this before e^(pi*i) gets back, factoring out x will actually give: $x \left ( 2 + 2\cos{x} - x\sin{x} \right )$ .

**FreaKariDunk** · February 26th 2011, 05:41 PM

Thank you y'all for all your help. All work and No play makes me grumpy. :P

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