Hi !

This is just curiosity.. : I'd like to know how you'd do it and what you're going tosay. I don't need the result.

$\displaystyle C(x)=\int_0^\infty e^{-t} \cos(xt) \ \frac{dt}{\sqrt{t}}$

$\displaystyle S(x)=\int_0^\infty e^{-t} \sin(xt) \ \frac{dt}{\sqrt{t}}$

Establish the equation :

$\displaystyle C'(x)=-x \cdot S'(x)-\frac 12 \cdot S(x)$