>>379
No, it was to get spherical coords (I mean longitude and latitude) of some plane cutting this sphere. 
It had parameters like:
-\[1\] - radius of shpere
-\[\lambda_0, \phi_0 \] - parameters of a point of a sphere which is intersection of a line perpendicular to the plane and sphere. 
-\[\alpha\] - where \[cos(\alpha)\] is distance from plane to the center of the sphere

I don't remember it now, but I remember that distance \[\delta\] from \[[0;0]\] to \[[\phi;\lambda]\] was something like this:

\[cos(\delta) = cos(\lambda)cos(\phi)\]

but I don't remember if it's really true even though it was a very nice and simple solution.