(A) cos((7pi )/(4))= Using the Unit Circle . find the exact value of this trig function. -(1)/(2) (sqrt (2))/(2) (1)/(2) The correct answer is not listed -(sqrt (2))/(2)

To find the exact value of , we can use the unit circle.The unit circle is a circle with a radius of 1, and it is used to represent the values of trigonometric functions for different angles.In the unit circle, the angle is located in the fourth quadrant. The cosine function represents the x-coordinate of a point on the unit circle.To find the exact value of , we can use the fact that the cosine function is positive in the fourth quadrant.The angle is equivalent to , which is the same as . This angle is in the fourth quadrant, and the cosine function is positive in this quadrant.The reference angle for is , which is a common angle in the unit circle. The cosine of is .Therefore, the exact value of is .So, the correct answer is .