Michael J. answered 07/27/15
Tutor
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Mastery of Limits, Derivatives, and Integration Techniques
We use the chain rule for this one. Notice that cotx is the argument of cosine. So we have to evaluate cotx first, then find the cosine of that result.
The formula for chain rule is derivative of the inner function times the derivative of the outer function evaluated inside.
First step: Derive the inner function, which is cotx.
-csc2x
Second step: Derive the outer function evaluated inside. This function is cos(x).
y' = -csc2x*(sinx(cotx))