# Math derivatives

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What is the derivative of:
a) cos(3x)
b) π/x

I did (a) just by following chain rule:
-sin(3x)*3
so it's -3sin(3x)

Is that correct?

I'm not completely sure how to do (b). Would it just be like the derivative of 1/x? That's -1/(x^2), would it be -π/(x^2) ?

• Math derivatives -

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