# Exponential Integral

1. Nov 5, 2009

### brandy

1. The problem statement, all variables and given/known data
i have to integrate e^(-y) / y
and i found out that you have to use this exponential integral and someone else said it doesnt have an integral. either way im thoroughly confused

3. 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.

2. Nov 5, 2009

### 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

3. Nov 5, 2009

### 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.