cosX cosY = (1/2) [ cos (X - Y) + cos (X + Y) ]
sinX cosY = (1/2) [ sin (X + Y) + sin (X - Y) ]
cosX sinY = (1/2) [ sin (X + Y) - sin[ (X - Y) ]
sinX sinY = (1/2) [ cos (X - Y) - cos (X + Y) ]
For example, when u = 13 o, v = 17 o, sin(13)sin(17) = 0.065769, cos(13)cos(17) = 0.931795, sin(13)cos(17) = 0.215122, cos(13)sin(17) = 0.284878.