# How do you differentiate #f(x)=cos(7-4x) # using the chain rule?

##### 1 Answer

Mar 24, 2016

#### Explanation:

The chain rule, when applied to

#d/dxcos(u)=-sin(u)*u'#

This is very similar to the typical differentiation for

#d/dxcos(x)=-sin(x)#

except for that when the chain rule is applied the derivative of the function

Applying this to

#f'(x)=-sin(7-4x)*d/dx(7-4x)#

Note that the derivative of

#f'(x)=-sin(7-4x)*(-4)#

#f'(x)=4sin(7-4x)#