# How do you differentiate #k(x)=-3 cos x#?

##### 1 Answer

Oct 26, 2016

You could start off by saying that:

y=k(x)

If this is the case:

Now from here you can use **implicit differentiation** to get

Which means that:

And this means that:

Realistically speaking, if you are studying differentiation, you've got to memorise:

If

This is very important.