That requires neither engineering-level math nor paper nor patience. All you need is the chain rule and some basic knowledge of sine and cosine:
The derivative of cos is -sin, but because of the 6x you get an extra factor 6. The sine function is periodic on 2pi, so sin(6*2pi + pi/2) = sin(pi/2) = 1. So the result is -36
BlueEther@no.lastname.nz 3 months ago
It’s been nearly 35 years since I did uni level calc and I’ve not really used in the the years since - fucked if I could figure it out without a lot of <insert search engine of choice> foo these days