find the integral(2)

**chialin4** · March 9th 2010, 04:46 AM

1. $\int\frac{sinx}{x}dx$
2. $\int_{-00}^{00} (cosx)e^{-x^{2}/2}dx$

**shawsend** · March 9th 2010, 04:48 AM

Originally Posted by chialin4

$\int\frac{sinx}{x}dx$

$\int \frac{\sin(x)}{x}dx=\text{SinIntegral(x)}$

. . . stop special function discrimination: equal rights for special functions.

**chialin4** · March 9th 2010, 05:13 AM

Originally Posted by shawsend

$\int \frac{\sin(x)}{x}dx=\text{SinIntegral(x)}$

. . . stop special function discrimination: equal rights for special functions.

???
what do u mean ?

**Miss** · March 9th 2010, 05:20 AM

Originally Posted by chialin4

???
what do u mean ?

You can not solve this integrals in terms of elementary function.
This well-known integral is used in electrical engineering.
See:
integrate sin(x)/x - Wolfram|Alpha

**shawsend** · March 9th 2010, 07:23 AM

Originally Posted by chialin4

???
what do u mean ?

Hi. It's a suggestion to treat "special functions" like antiderivatives of integrals that can't be expressed in simple terms, in the same way that you treat $\sin(x)$ so if I have $\int \cos(x)dx$ you say "hey, that's easy, it's $\sin(x)$ . So hey, $\int \frac{sin x}{x}$ is easy. It's . . .

Also, for that second we did that one here:

http://www.mathhelpforum.com/math-he...x-e-x-2-a.html

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