How do i find the derivative of (1+2cos(theta))(cos(theta)) ?

Question

anonymous · Answer

deriv (1+2cos(t))*(cos(t)+(1+2cos(t)*deriv(cos(t)

miracrown · Answer

deriv (1+2cos(t))*(cos(t))+(1+2cos(t)*deriv(cos(t)
Was missing a paren.

So, I think you're applying chain rule correctly

miracrown · Answer

Two multiplicative terms ... derivative of them is
(first * deriv of second) + (second * deriv of first)

Do you know deriv of cos?

miracrown · Answer

It is -sin. What about deriv (1 + 2cos(t))?
What would that be?

miracrown · Answer

Your participation is just as important as my help.

anonymous · Answer

Rusty on the rules, but i see it's the product rule here.  However when I try to get the derivative of (1+2cost) I get (t-2sint), is this right?  Because from here out it sways me away from the correct answer (which I already know, just not sure how to get there)

anonymous · Answer

sorry was on another tab trying to look for answers

miracrown · Answer

That's alright. :) 
deriv of (1 + 2cost) = 0 - 2sint
(deriv of 1 = 0, deriv of any constant = 0)

anonymous · Answer

Ha!  Was thinking of integrals.  Ok working on it now

anonymous · Answer

Got it :)  Thanks a million!

miracrown · Answer

Yw (: