1) sin(-23Pi/3) = sin(-21Pi/3 - 2Pi/3) = sin(-7Pi-2Pi/3) = -sin(7Pi+2Pi/3) = -sin(Pi+2Pi/3) = sin(2Pi/3) = sqrt(3)/2
2) cos(25Pi/6) = cos(24Pi/6+Pi/6) = cos(4Pi + Pi/6) = cos(Pi/6) = sqrt(3)/2
18 / (sqrt(3)/2)*(sqrt(3)/2) = 18 / 3/4 = 18*4/3 = 24
Ответ: 24