Question

Differentiate log cos ​

Answer 1

Remember that the derivative of lnu=1u=1cosx . Now we just need to find the derivative of the inner function, cosx , and multiply it by the derivative of the outer function we just found. Since the derivative of cosx is ( −sinx ), we end up with: dydx=(1cosx)⋅(−sinx)=(−sinxcosx)=−tanx .