Question

How do you find the stationary points of the function `y=cos(x)`?

Answer 1

`y=cosx`

By taking the derivative,

`y'=sinx=0 Rightarrow x=npi`, where `n` is any integer

Since `y(npi)=cos(npi)=(-1)^n`,

its stationary points are `(npi,(-1)^n)` for every integer `n`.

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I hope that this was helpful.