Final answer:
The value of cos (7π/4) is -√2/2, and the value of sin (7π/4) is -√2/2.
Step-by-step explanation:
To find the value of cos (7π/4) and sin (7π/4), we can use the unit circle. In the unit circle, the angle 7π/4 is in the third quadrant. The cosine value in the third quadrant is negative, and the sine value is also negative.
Therefore, cos (7π/4) = -√2/2 and sin (7π/4) = -√2/2