解:令y=xt,则dy=xdt+tdx代入原方程,化简得 2tcostdx=x(tsint-cost)dt==>2dx/x=(sint/cost-1/t)dt==>2dx/x+d(cost)/cost+dt/t=0==>2∫dx/x+∫d(cost)/cost+∫dt/t=0==>2ln│x│+ln│cost│+ln│t│=ln│C│ (C是常数)。==>x^2*t*cost=C==>xycos(y/x)=C故原方程的通解是xycos(y/x)=C。