求不定积分∫lnxdx和∫1/(e^x+e^-x)dx

问题描述:

求不定积分∫lnxdx和∫1/(e^x+e^-x)dx

1.直接用分部积分,xlnx-x+C 2.化为:∫e^x/(e^2x+1)dx =∫d(e^x)/(e^2x+1) 设e^x=t,那么得:=∫dt/(t^2+1) =arctant+C =arctan(e^x)+C