Exponential Integral Homework: Integrating e^(-y)/y

[brandy]

Homework Statement

i have to integrate e^(-y) / y
and i found out that you have to use this exponential integral and someone else said it doesn't have an integral. either way I am thoroughly confused

The Attempt at a Solution

i have no clue what so ever. The original question had it in dy/dx=y*e^(x+y) but that above question is all i need help with.

 

[tiny-tim]

Hi brandy!

(try using the X² tag just above the Reply box )

If you keep integrating by parts, you get a power series times e^-y

 

[Bohrok]

\int\frac{e^{-y}}{y}dy = \int-\frac{e^{-y}}{-y}dy

Let x = -y, then dx = -dy.

\int-\frac{e^{-y}}{-y}dy = \int\frac{e^x}{x}dx

You can rewrite it as the same integral you had in the other thread, which still doesn't have an elementary integral.