# Derivation of f(x)=xcos(sen(x)) – 1

Hi Could someone help me derivating this function:

f(x)=xcos(sen(x)) – 1
f'(x)= ?
f''(x)= ?

Thank you.

I like Serena
Homework Helper
Hi Could someone help me derivating this function:

f(x)=xcos(sen(x)) – 1
f'(x)= ?
f''(x)= ?

Thank you.

What kind of function is sen(x)?
Or did you mean sec(x)?

If that sen(x) is indeed a sec(x) then just use the product rule between x and cos(sec(x)). The -1 becomes 0. When you get the new function derive it again and you'll have f''(x).

You might be asking for the answer in which case I won't be giving you because you'll never learn it yourself.

Woops. Just realized that mistake I made. That was embarrassing.

Last edited:
What kind of function is sen(x)?
Or did you mean sec(x)?

sorry, its "sin(x)"

Mark44
Mentor
You are going to need to use the product rule and the chain rule, in that order.

BTW, there is no such word as "derivating" in English, and I doubt that it is a word in any other language. To find the derivative of a function, we differentiate the function - we don't "derivate" it or "derive" it.

Starting with ax2 + bx + c = 0, I can derive the Quadratic Formula, but this has nothing to do with differentiation.