How do you use the chain rule to differentiate #f(x)=ln(cosx)#?

1 Answer
Pablocito
Jul 3, 2017
  • tan x

Explanation:

Derivative ln (cos x)
Note Derivative ln x = 1 / x
So Derivative ln (cos x) = 1 / cos x
But we must also take the derivative of the argument [cos x]
which is - sin x
Thus
Derivative Ln (cos x) = - sin x / cos x = - tan x

You can check this by Integrating -tan x
with U Substitution to obtain Ln (cos x)

Related questions
See all questions in Chain Rule
Impact of this question
1326 views around the world
You can reuse this answer
Creative Commons License