# Exponential Integral

#### brandy

1. 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 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.

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#### tiny-tim

Homework Helper
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.