find the derivative of y=cos pix/sinpix+cospix
Let u = pi * x
cos u/sin u = cot u
so d/dx cot u = -csc^2 u * du/dx = -pi * csc^2 pix
d/dx cos pix = -pi * sin pix
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cos u/sin u = cot u
so d/dx cot u = -csc^2 u * du/dx = -pi * csc^2 pix
d/dx cos pix = -pi * sin pix
...