Find angles x and y, each between 0 and 90 degrees,
which satisfy the simultaneous equations
\(\displaystyle \cos x \cos y = 0.6, \\ \displaystyle \sin x \sin y \, = 0.2.\)
cosxcosy - sinxsiny = cos(x + y) = 0.6 - 0.2 = 0.4, x + y = arccos(0.4).
cosxcosy + sinxsiny = cos(x - y) = 0.6 + 0.2 = 0.8, x - y = arccos(0.8).
etc.
