Question

If f(x)=x4cosx, then f′(x)=

Answer 1

you will need the product rule

if

\[y = f(x) \times g(x)\]

then

\[\frac{dy}{dx} = f(x) \times g'(x) + g(x) \times f'(x)\]

so let

\[f(x) = x^4 ..... and ....g(x) = \cos(x)\]

can you find the derivative of f(x) and g(x)

Answer 2

?

Answer 3

xcos(4) ?

Answer 4

umm do you know about the product rule.

and is the inital function correct..?

Answer 5

yes

Answer 6

oops

let

\[g(x) = x^4\]

and

\[h(x) = \cos(x)\]

what are the derivatives of g(x) and h(x)

Answer 7

g'(x).h(x)+g(x).h'(x)

Answer 8

thats it... thats the product rule