# The Calculus Chain Rule

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The Chain Rule is one of those Calculus rules that you have to always have in the back of your mind when you are doing differentiation. When we have two functions there are several ways that we can combine those two functions to create another function. We can add them, subtract them, multiply them, or divide them. Another way you can combine two functions is by Function composition. Function composition is used to describe and summarize complex dependencies in nature. For example, when sea temperatures rise there are less krill. Because there are less krill there is less food for blue whales to eat. Function composition in this example allows us to directly determine the blue whale population as a function of sea temperature.

Once we have combined two functions by function composition we can then find the derivative. To do this directly is sometimes impossible. The chain rule allows us to differentiate a function composition very quickly and very easily. Our lesson on the Chain Rule is visible for everyone to see so take a moment to check it out for FREE. The great thing about this rule is that it is easy to memorize and can be used to solve very difficult derivatives. This rule is a part of every Calculus class so if you haven't seen it yet then you most certainly will soon.