# Thread: Differentiate the following function

1. ## Differentiate the following function

Differentiate the following function. f (x) = 7 x 3 - 6 cos(x)
f ' (x) =

Attempt:

21x^2 - 6sin(x)

Please help me! thank you!

2. Originally Posted by miss.strw
Differentiate the following function. f (x) = 7 x 3 - 6 cos(x)
f ' (x) =

Attempt:

21x^2 - 6sin(x)

Please help me! thank you!
HI

you made a sign error

Should be 21x^2 + 6 sin x

Remember when you differentiate cos , you get - sin .