Подстановка условия
[src]cos(a - pi/6) - sin(a)/2 при a = 3/2
−21sin(a)+cos(a−6π) cos((3/2) - pi/6) - sin((3/2))/2
−21sin((3/2))+cos((3/2)−6π) cos(3/2 - pi/6) - sin(3/2)/2
−21sin(23)+cos(−6π+23) -sin(3/2)/2 + sin(3/2 + pi/3)
−21sin(23)+sin(3π+23)