This is a really good problem on applying the Chain Rule multiple times. We start by making sure that you understand the power notation for trig functions. Once we see this we can identify the outer and inner functions and apply the Chain Rule the first time by using the shortcut that I call the General Power Rule. We then apply the Chain Rule again to find the derivative of cos(3x). This is a standard question for calculus 1 so we cover everything you need to get through this.
Shortcuts for the Chain Rule - General Power Rule and General Exponential Rule: https://youtu.be/3Sl4Hvm3rRk
Chain Rule Multiple Times Problem 1: https://youtu.be/b7tHudJjgDU
Chain Rule Multiple Times Problem 3: https://youtu.be/LMQrRgTXQYE
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https://www.blacktshirtmathprofessor.com/videos
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