teX :: Double -> (Double, Double, Double) -> (Double, Double, Double)
rotateX a (x, y, z) = (co * x + si * z, y, co * z - si * x)
   where co = cos a
         si = sin a

ro
rotateX :: Double -> (Double, Double, Double) -> (Double, Double, Double)
rotateX a (x, y, z) = (co * x + si * z, y, co * z - si * x)
   where co = cos a
         si = sin a
rotateX a (x, y, z) = (co * x + si * z, y, co * z - si * x)
   where co = cos a
         si = sin a