Given the rectangular coordinates (2,-2√3), which of the following polar coordinate pairs in radians represents the same point?

a. (-4, 2π/3)
b. (4, 4π/3)
c. (-2, π/3)
d. (2, 5π/3)

The magnitude of this point is , so the magnitude is four.  

We can finish the solution by trying the only two answers with magnitude four: A and B.

For option B, the rectangular coordinates are , so B is incorrect.

For option A, the rectangular coordinates are , so the answer is A.