Sin (30+a) - cos (60+a) / sin (30+a) + cos (60+a) =

1. sin (30°-a) - sin (60°-a) = sin (30°) cos (a) - cos (30°) sin (a) - (sin (60°) cos (a) - cos (60°) sin (a)) = 1/2*cos (a) - sqrt (3) / 2*sina-sqrt (3) / 2*sin (a) + 1/2*cos (a) =

=cos (a) + √3cos (a)

2. sin (30-a) - cos (60-a) = sin30*cos (a) - sin (a) * cos30-cos60*cos (a) - sin60*sin (a) = cos (a) / 2-√3*sin30/2-cos (a) / 2-√3*sin (a) / 2=√3*sin30/2-√3sin (a) / 2.

3. cos (a) + √3cos (a) / √3*sin30/2-√3sin (a) / 2