[x√(1-y²)]dx+[y√(1-x²)]dy=0[y√(1-x²)]dy＝-[x√(1-y²)]dx分离变量得 ydy/√(1-y²)=-xdx/√(1-x²)取积分得：-(1/2)∫d(1-y²)/√(1-y²)=(1/2)∫d(1-x²)/√(1-x...