3D Asteroids Movement Question

Blitz3D Forums/Blitz3D Beginners Area/3D Asteroids Movement Question

OK, well if you remember, I made a 2D asteroids game a while ago. Now, as my first step in to 3D, I'm remaking that game in 3D, except I'm only using the x and z axis so you can't move in all 3 dimensions, but it's made of meshes. So anyways,I'm having trouble with the ship physics. In my 2D version, I used this to find the direction the ship should move based on the way it's facing:
dx#=dx#+Sin(dir#)*speed#
dy#=dy#+Cos(dir#)*speed#

Then I would add dx# to the player's x and dy# to the player's y.
I tried to apply this to the 3D version:
pdx# = pdx#+Sin(-EntityYaw(ship))*pds#
pdy# = pdy#+Cos(-EntityYaw(ship))*pds#

Then I add pdx# to px#(player's x) and pdy# to py#(player's z which I treat as a y since I'm only using 2 dimensions)
The whole 'y' part of it works fine, but I'm having a problem with the 'x' part. pdx# ends up as very weird numbers i.e 3.23464e-006, therefore px# ends up a weird number like that and when I position the ship at px# it just stays at 0, I'm guessing because it can't position itself at 3.23464e-006 or a number like that.
Why is this and what can I do to fix it?