Trigonometry

I'm using:

PostgreSQL 6.3.2 on i686-pc-linux-gnu, compiled by gcc 2.7.2.3
('cuz that's what my ISP gots)

and there don't seem to be any trigonomeric functions, so I'm really up a
creek for trying to calculate latitude/longitude distances using:

create function radians(float4) returns float4 as
'select 3.1415927 * $1 / 180'
language 'sql';

create function gpsdistance(float4, float4, float4, float4) returns float4 as
'select (3590 * (2 * atan2( sqrt(pow((sin(radians(($1 - $3))/2)),2) +
cos($4) * cos($2) * pow((sin(radians(($2 - $4))/2)),2)),
sqrt(1-(pow((sin(radians(($1 - $3))/2)),2) + cos($4) * cos($2) *
pow((sin(radians(($2 - $4))/2)),2))))))'
language 'sql';

The online docs don't seem to have anything about trig nor longitude
latitude, but I could have sworn somebody said that kind of stuff was in
PostgreSQL...

Any ideas, keeping in mind that installing a new PostgreSQL or adding stuff
to it that requires being root or even postgres super-user are not an
option?...

I *can* compile c code, so if somebody could 'splain to a Lisp hacker how
to make a gpsdistance.so that would maybe work?

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