Well, you should really take a negative out of the cos because cos(-theta) = cos(theta)Wait, how do you find the modulus of (cos(pi/6) - isin(pi/6))?
and a negative into sin: -sin(theta) = sin(-theta)
So it becomes cos(-pi/6) + isin(-pi/6) = cis(-pi/6)
And therefore the modulus is 1 because there is no coefficient before the cis.