How solve this trigo system ?

[Dieter]

(09-18-2017 08:56 AM)ggauny@live.fr Wrote:  cos x - cos y = 1/2
sin x * sin y = 3/8

Finally, you may try wolframalpha.com to solve this. Simply enter
solve (cos x - cos y = 1/2) AND (sin x * sin y = 3/8) for x,y

The returned results include some nice (x,y) plots that show multiple sets of two ring-shaped graphs with four intersections each. Very illustrative, I think.

Dieter