# Calculus Derivatives (confused)

• Sep 18th 2009, 10:15 AM
Marker
Calculus Derivatives (confused)
I under stand the chain rule and all.. but I have never seen derivatives envolving trig fuctions.

I have g(x)=x^2cos(x)

so is this right?

2*X*cos(x)
so
2xcos(x)

Really confused, would greatly appreciate it if someone could guide me through the problem.
• Sep 18th 2009, 10:34 AM
Plato
Quote:

Originally Posted by Marker
but I have never seen derivatives envolving trig fuctions.

I have g(x)=x^2cos(x) so is this right?
2*X*cos(x)
so
2xcos(x)

No it is not correct.
You statement is very hard to believe.
You do have a textbook. The derivatives of trig functions are discussed in it.
Look them up.
• Sep 18th 2009, 10:40 AM
Marker
I don't have my text book.

but I figured it out.

• Sep 18th 2009, 03:08 PM
mr fantastic
Quote:

Originally Posted by Marker
I under stand the chain rule and all.. but I have never seen derivatives envolving trig fuctions.

I have g(x)=x^2cos(x)

so is this right?

2*X*cos(x)
so
2xcos(x)

Really confused, would greatly appreciate it if someone could guide me through the problem.

Is it g(x)=x^(2cos(x)) or g(x)= (x^2) cos(x). If the latter, use the product rule and note the advice given earlier.
• Sep 18th 2009, 04:31 PM
Marker
it was the latter, but I figured it out. Thanks anyway.