v=-1/25*cos(25*y)
-1/25*cos(25*y)*u'=sin(50*y)
du/dy=-25*sin(50*y)/cos(25*y)
int du=int -25*sin(50*y)/cos(25*y)dy
u=2*cos(25*y)
x=-1/25*cos(25*y)*2*cos(25*y)=-2/25*(cos(25*y))^2


спасибо за помощь