例2求∫ rnx 解 d(ln x) xnx Inx du u=Inx =Inu+c In Inx+c Economic-mathematics 48-8 Wednesday, February 24, 2021Economic-mathematics 48- 8 Wednesday, February 24, 2021 例2 求 . ln 1 dx x x  解 dx x x  ln 1 (ln ) ln 1 d x x  = =  du u = ln x u 1 = lnu +C = lnln x +C