#3. 25
(u*v)`=u`*v+u*v` u=ctg(1/x) u`=(-1/sin^2(1/x))((1/x)`=(-1/sin^2(1/x))*(-1/x^2)=1/(x^2*sin^2(1/x)) v`=(arccosx^4)`=-(x^4)`/sqrt(1-(x^4)^2)=-4x^3/sqrt(1-(x^4)^2) О т в е т. (1/(x^2*sin^2(1/x))) * arccos(x^4) + (ctg(1/x)) * (4x^3/sqrt(1-x^8))