Final answer:
Logarithmic differentiation is mainly used to simplify the differentiation of products or quotients involving variables and is especially helpful for functions with variable exponents.
Step-by-step explanation:
Logarithmic differentiation should be used c) to differentiate products or quotients involving variables. This method is particularly useful when you have functions raised to a power that itself is another function or when differentiating variable expressions in the exponent. By taking the logarithm of both sides of an equation, you can use properties of logarithms to simplify the differentiation process, such as turning products into sums, quotients into differences, and powers into products.
The usefulness of logarithmic differentiation is not limited to these examples. It can also help when dealing with exponential functions and their inverses (like in equilibrium problems involving roots), or when the function's algebraic manipulation is otherwise complex.