The correct answer is A) 0.778.
The value of cos(a) cannot be 0.778 because the maximum value of cos(a) is 1, and 0.778 is greater than 1.
Here's why the other options are incorrect:
- B) (1-√3)/2 is approximately -0.366, which is a valid value for cos(a).
- C) √2 - 1 is approximately 0.414, which is also a valid value for cos(a).
Note: cos(a) can have any value between -1 and 1.
