Improper integrals: (e^x) / (e^x -1) from -1 to 1, etc.

[paulxzt]

1) Integral of (e^x) / (e^x -1) from -1 to 1.
2) Integral of (2+e^-x)/(x) from 1 to infinity
3) Integral of e^-x / sqrt(x) from 0 to 1.

can someone please help me on how to start problems like these..

1) should I use the u substitution?

2) do I have to integrate this by the improper integral definition? cause 0 is not in the bounds, should i just use integration by parts? '

3) don't know how to start

thanks for any help.

 

[royhaas]

1) Yes
2) Infinity is a "bound"
3) \(\displaystyle u=\sqrt{x}\)