Recent content by ThaSlave

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    Undergrad Def. of derivative and cosx=sin(Pi/2-x) to prove y'=-sinx

    A lot of web pages/books show how to use cosx=sin(Pi/2-x) and the chain rule to prove that the derivative of cosx=-sinx. My question is how to use this identity and the definition of the derivative to prove the same thing. Or whether it is at all possible. Seeing that i get...