Question

Find the value of the derivative (if it exists) at each indicated extremum. (If an answer does not exist, enter DNE.)

f (x) = cosπx/2

Answer 1

The derivative of cos(ax) is
-a*sin(ax)
So here we have a=pi/2 so
d/dx(cos(pi*x/2))=-(pi/2)sin(pi*x/2)