How do you find the derivative of #ln(cosx)#? Calculus Differentiating Trigonometric Functions Derivative Rules for y=cos(x) and y=tan(x) 1 Answer Jim H Oct 9, 2015 Use the derivative of #ln# and the chain rule. Explanation: #d/dx(lnu) = 1/u d/dx(u)# So #d/dx(ln(cosx)) = 1/cosx d/dx(cosx)#. You can finish this. Answer link Related questions What is the derivative of #y=cos(x)# ? What is the derivative of #y=tan(x)# ? How do you find the 108th derivative of #y=cos(x)# ? How do you find the derivative of #y=cos(x)# from first principle? How do you find the derivative of #y=cos(x^2)# ? How do you find the derivative of #y=e^x cos(x)# ? How do you find the derivative of #y=x^cos(x)#? How do you find the second derivative of #y=cos(x^2)# ? How do you find the 50th derivative of #y=cos(x)# ? How do you find the derivative of #y=cos(x^2)# ? See all questions in Derivative Rules for y=cos(x) and y=tan(x) Impact of this question 1746 views around the world You can reuse this answer Creative Commons License