The reference angle is the angle made with the x-axis. For two points to have the same reference angle, they would need to have the same absolute value of their tangents = y/x. For the first pair of points: the first point has a tangent value of 1/sqrt(3), while the second has a tangent value of sqrt(3), so these are not identical. For the second pair of points: the first point has a tangent value of -sqrt(3), while the second has a tangent value of -1/sqrt(3), so these are
not identical. For the third pair of points: the first point has a tangent value of sqrt(3), while the second also has a tangent value of sqrt(3), so these have the same reference angle. For the fourth pair of points: the first point has a tangent value of
1/sqrt(3), while the second has a tangent value of sqrt(3), so these are
not identical.
