To simplify this expression, we need to evaluate the cosine and sine of the given angles.
cos( -π/3) = cos( -60°) = 1/2sin( -π/6) = sin( -30°) = -1/2
Now we can substitute these values into the expression:
-18√3 (1/2) (-1/2)= -18√3 * (-1/4)= 18√3/4= 9√3/2
Therefore, the simplified expression is 9√3/2.
To simplify this expression, we need to evaluate the cosine and sine of the given angles.
cos( -π/3) = cos( -60°) = 1/2
sin( -π/6) = sin( -30°) = -1/2
Now we can substitute these values into the expression:
-18√3 (1/2) (-1/2)
= -18√3 * (-1/4)
= 18√3/4
= 9√3/2
Therefore, the simplified expression is 9√3/2.