Answer:
A
Step-by-step explanation:
From the ASTC circle, we know that in the third quadrant where the variable is equal to 7π/6, the value obtained will be negative.
The cosine of the related angle π/6 gives a value of [tex]\frac{\sqrt{3} }{2}[/tex] .
Since we know that it will be negative in the third quadrant, this means that it will be the negative of the cosine for the related angle.
Thus, the answer is A.
