The solution of the differential equation xx2+y2dy=yx2+y2−1dx is
y=xcot(c-x)
9cos-1(y/x)=c-x
y=xtan(c-x)
y2x2=xtan(c-x)
xdy−ydxx2+y2=−dx⇒∫dTan−1(y/x)=−∫dx⇒Tan−1(y/x)=-x+c⇒y=xtan(c−x)