its asking what the partial derivative of 4Sin(7x - pi/2) is when x = 0
the partial derivative of sin(x) is cos(x) and by the chain rule:
d/dx = 4*Cos(7x- pi/2)* 7 which simplifies to 28Cos(-pi/2) at x = 0
and 28Cos(-pi/2) = 0
Ooor you could just do the calculus before integrating and you get d/dx=4 (or some other constant if i made a mistake). And partial integral of a constant is always 0.