Answer:
The exact value of cos(7π/6) can be found using the unit circle. 7π/6 is equivalent to 210 degrees, which places the angle in the third quadrant of the unit circle. The reference angle for 7π/6 is π/6 or 30 degrees. The cosine of an angle in the third quadrant is negative, so cos(7π/6) = -cos(π/6). Since cos(π/6) = √3/2, we have cos(7π/6) = -√3/2.
Explanation: