BUG #4749: trigonometric functions broken

The following bug has been logged online:

Bug reference:      4749
Logged by:          Stefano Salvador
Email address:      stefano.salvador@gmail.com
PostgreSQL version: 8.3.7
Operating system:   Linux
Description:        trigonometric functions broken
Details:

try:

   select sin(pi());

returns: 1.2246

or:

   select cos(pi()/2);

returns: 6.123


but sin and cos are limited between -1 and 1 !!!

I suspect than tan() function is broken too.