问答题
已知ysin x-cos(x-y)=0，求dy．
【正确答案】
【答案解析】利用一阶微分形式的不变性求得d(ysinx)-a[cos(x-y)]=0，即
sinxdy+ycosxdx+sin(x-y)(dx-dy)=0
整理得
[(sin(x-y)-sinx)]dy=[ycosx+sin(x-y)]dx
故
sinxdy+ycosxdx+sin(x-y)(dx-dy)=0
整理得
[(sin(x-y)-sinx)]dy=[ycosx+sin(x-y)]dx
故