(PHP) Generate / Create (pseudo) random numbers between -1 and 1

<?php
/**To generate (pseudo) random numbers in range of -1 and 1 you can use the cosine
 * that will return a number in range of -1.0 and 1.0.
 *
 * Note for nerds:
 * It's not a real big problem that the cosine is deterministic due to the fact that mt_rand isn't really perfect, too. Hence this is PSEUDO random number generation.
 */
$r = cos( mt_rand() );

// In case your mt_rand() implementation returns (for whatever reason) values between 0.0 and 1.0 go with:
$r = cos( mt_rand() );
if( intval( mt_rand() ) % 2 == 0 ) // Switch sign randomly
  $r = -$r;
?>
Bitcoin:	1QC38uPBSy7WSYz1whM5SYTHAdhqkN6o8V
Ethereum:	0x0855778a6181a69cc7d5d08c71c4f5846010eb67
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Date posted:	Wed, 18 Jan 2012 22:26:01 +0000
Date of expiration:	never (permanent entry)
Description:	(PHP) Generate / Create (pseudo) random numbers between -1 and 1