Use Chain Rule instead of Product Rule

In some occasions, Chain Rule can be applied instead of Product Rule. Look at the example below:

Find the derivative of f(x)=sec3x

If you use product rule, you will get (secx*tanx)*secx*tanx+secx(secx*tanx)+secx*secx*(secx*tanx)=3sec3x*tanx

But that uses more time than just doing a simple chain rule. Here, f(x) can be think of the composition of two functions -- a secant function and a function to the 3rd power.


So by using chain rule instead, we get this:



  • Subject : Math
  • Topic : Calculus
  • Posted By : Jason

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