// α β

   x = r cosα

   y = r sinα

   x' = r cos (α+β)

   y' = r sin (α+β)

   x' = r (cosα cosβ - sinαsinβ)

   y' = r (sinαcosβ + cosαsinβ)

   x' = xcosβ - ysinβ

   y' = xsinβ + ycosβ

   z = z'