交换积分次序原式=∫y²dy∫sin(xy)dx (0≤y≤1，-√(1-y²)≤x≤√(1-y²))=∫y[-cosy√(1-y²+cosy√(1-y²+]dy (0≤y≤1)=∫0dy (0≤y≤1)=0
