f(x) = sqrt(3) sinxcosx - 1/2 - 1/2 cos2x - 1/2 = sin(2x-pi/6) - 1
f(C) = 0, 2C-pi/6 = pi/2
C = pi/3
c = 3
sinA = sinB/2 = sinC/c = sqrt(3)/6, sinB = sqrt(3)/3
a = c * sinA/sinC = 3 * sqrt(3)/6 / sqrt(3)/2 = 1
b = c sinB/sinC = 3*sqrt(3)/3 / sqrt(3)/2 = 2