5.41 Problem 12.4 chapter 4, Boas book

restart; 
z:=   Int( sin(t)/t, t=sin(x)..cos(x)); 
diff(z,x);
 

\[ -{\frac {\sin \left ( x \right ) \sin \left ( \cos \left ( x \right ) \right ) }{\cos \left ( x \right ) }}-{\frac {\cos \left ( x \right ) \sin \left ( \sin \left ( x \right ) \right ) }{\sin \left ( x \right ) }} \]