Logarithmic Differentiation#
Compute Derivatives using Logarithmic Differentiation
The process of logarithmic differentiation can be used to compute the derivative of any function, but is particularly useful when the function involves products, quotients, and/or powers that can be expanded using laws of logarithms. Starting with:
the process of logarithmic differentiation is carried out in the following manner.
Take the natural logarithm of both sides of the above equation and use the properties of logarithms to expand
.Differentiate both sides (implicitly on the left-hand side, explicitly on the right-hand side) of the equation with respect to
. In particular, notice that:Solve the resulting equation for
(by multiplying both sides by ) and then replace with .
Example 1#
Logarithmic differentiation
Compute the derivative of
Step 1: Observe that involves products, quotients, and powers.
While
Step 2: Take the natural logarithm and expand.
Take the natural logarithm of both sides of
Step 3: Differentiate both sides.
Recall
Step 4: Solve for .
Multiply both sides by
Example 2#
Logarithmic differentiation
Compute the derivative of
Step 1: Recognize the form of .
Observe that
Step 2: Take the natural logarithm and expand.
Take the natural logarithm of both sides of
Step 3: Differentiate both sides.
Recall
Step 4: Solve for .
Multiply both sides by