How do I work out vertex coordinates after rotation

Ok,

I have manually created a face with 4 vertices.

If x,y=0 then the vertices would be created at (-1,-1 : -1,1 : 1,1 : 1,-1)

This therefore means that the angle of point x,y is 0

Say i wanted to rotate 30 degrees the center point x,y, how would I manually calculate the position of the 4 vertices. Obviously it is a SIN/COS thang, but any examples?

(This is for a single surface particle system i am doing)

Cheers

Rob

Sorry, just worked it out, here is the code if you're interested

graphics3d 320,240,16,3

x=160
y=120

dist=1
angle#=0

while not keyhit(1)
      cls
      plotdot(x,y,angle,-10,-10)
      plotdot(x,y,angle,-10,10)
      plotdot(x,y,angle,10,10)
      plotdot(x,y,angle,10,-10)

      if kEyhit(57)
            angle = angle + 9
      end if
      flip
wend
end

function plotdot(x,y,angle#,xadd=1,Yadd=1)

      new_x# = x + (xadd * cos(angle) - yadd * sin(angle))
      new_y# = y + (yadd * cos(angle) + xadd * sin(angle))
      color 255,255,255
      plot new_x,new_y

end function

Don't forget a lookup table for speed :)

Thanks Rob, that was my next step :)