积分区域是圆S=πf(x,y)=1/π, -√(2y-y²)<= x<=√(2y-y²),0<=y<=2fY(y)=∫(-∞,+∞)f(x,y)dx=2√(2y-y²),0<=y<=2如有意见,欢迎讨论,共同学习;如有帮助,请选为满意回答!