Differentiate the following function u = Cos(x3)

 u = Cos(x3)

To differentiate this function we will use the chain rule. Firstly we will set xto another variable name such as v. So now v = x3 . Lets differentiate this. dv/dx = 3x2

We can now differentiate cos(v) du/dv = -sin(v). Now to complete the chain rule we must do dv/dx*du/dv. Which will be -sin(v)*3x= -3x2sin(v). Now we can just put the x3 back in instead of the v and our final answer will be -3x2sin( x3).

SB

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