>>156

部分積分で
∫ log(xx+2) dx = x･log(xx+2) - ∫ 2xx/(xx+2) dx
　= x･log(xx+2) + ∫{4/(xx+2) -2} dx
　= x･log(xx+2) + (2√2)∫1/(tt+1) dt -2x
　= x･log(xx+2) + (2√2)arctan(t) -2x
　= x･log(xx+2) + (2√2)arctan(x/√2) -2x,

0→√2 で積分すると
　(2√2){log(2) + π/4 -1} = 1.35353063127