SOLUTION: If f(x)=cos nx, find f^(4)[pi/n]

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Question 460227: If f(x)=cos nx, find f^(4)[pi/n]
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Find the fourth derivative by finding all the other derivatives using the chain rule (there is a pattern).









At x = pi/n,