y看做常数令x=ytanu,则：(x²+y²)^(3/2)=y³sec³u,dx=ysec²udu∫1/(x²+y²)^(3/2))dx=∫ ysec²u/(y³sec³u) du=(1/y²)∫ cosu du=(1/y²)sinu + C=(1/y...