Can you help me differentiate this? I am checking to see if your result matches mine http://screencast.com/t/243ay4v0o

Question

Can you help me differentiate this? I am checking to see if your result matches mine   http://screencast.com/t/243ay4v0o

christos · Answer

anonymous · Answer

wait.....its 8xsinsx

hartnn · Answer

lol no! :P
you'll need product rule.

christos · Answer

Yea I could have sworn too. UNtil I found out that its wrong indeed

anonymous · Answer

oh yeah..yeah right
i forgot

christos · Answer

WHy do we need the product rule @Callisto ?

hartnn · Answer

tell us what you got ?

christos · Answer

8xsinx

anonymous · Answer

its 4x^2sinx-8xcosx

callisto · Answer

You are differentiating product of two variables :|
$$[f(x)g(x)]' = f(x) g'(x) + f'(x)g(x)$$

anonymous · Answer

is it correct?..i did it by product rule

anonymous · Answer

yeah....same thing...u get 4x^2sinx-8cosx

hartnn · Answer

yeah, you need product rule because you have 2 different functions, one trigonometric and one algebraic.

hartnn · Answer

@Christos will you try using the formula Callisto gave you ?
you'll basically have 2 terms....

christos · Answer

Yes I will try to do it right now

hartnn · Answer

:)
and we will verify it for you ;)

christos · Answer

The thing I dont understand is: is it wrong to just try and differentiate it the traditional way?

hartnn · Answer

traditional way ? 
i can't think of any traditional way to differentiate that.

christos · Answer

I see


So, my result is:   4x^2sinx-8xcosx

hartnn · Answer

yes :)

christos · Answer

yay!