http://hyperphysics.phy-astr.gsu.edu/hbase/rotv.html http://hyperphysics.phy-astr.gsu.edu/hbase/rotv.html Rotation Vectors http://hyperphysics.phy-astr.gsu.edu/hbase/rotv.html#rvec2 http://hyperphysics.phy-astr.gsu.edu/hbase/rotv.html