Derivative of cos(e^-θ^2) using the chain rule | Power and exponential rules

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Homework Statement


Find the derivative of the following

cos(e^-θ^2)


Homework Equations


cos=-sin
e^x=e^x
power rule


The Attempt at a Solution


So I have gotten this far: -sin(e^-θ^2) * ... but then i don't know where to go. Would I treat the -θ^2 as the next step inwards? My best guess would be this:

-sin(e^-θ^2) * e^-2θ * e^-θ^2
 
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This is chain rule inside of the chain rule.

So, {\cos(e^{-θ^2})} let u=e^{-θ^2} to find du, letv=-θ^2dv=-2θd{\theta} so du=-2θe^{-θ^2}d{\theta} and finally {\frac{d({cos(u)})}{du}=-{sin(u)}du}
 
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Perfect
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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