Asked by Joesph

z=cos(4 theta)

what is the derivative.

I know that the derivative of cos is -sin, but what do i do with the 4 theta. does that just become 4?
Answered by Reiny
dz/d(theta) = -sin(4theta) * 4
= -4sin(4theta)

in general if
y = cos u
then dy/dx = -sin u (du/dx)

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