To find the answer to the equation, you must substitute the options and see which of all meets the equality.
Substituting we have:
2 * COS ((0) * (PI () / 180)) ^ 2-COS (0 * (PI () / 180)) - 1 = 0
2 * COS ((150) * (PI () / 180)) ^ 2-COS (150 * (PI () / 180)) - 1 = 1.366025404
2 * COS ((180) * (PI () / 180)) ^ 2-COS (180 * (PI () / 180)) - 1 = 2
2 * COS ((210) * (PI () / 180)) ^ 2-COS (210 * (PI () / 180)) - 1 = 1.366025404
Therefore, the correct answer is 0
