y=1/2x,y=1/x的交点是(√2,√2/2)
x=2,y=1/x的交点是(2,1/2)
转化为定积分
∫[0,√2]1/2xdx+∫[√2,2]1/xdx
=1/4x^2[0,√2]+lnx[√2,2]
=1/2+1/2ln2