180*(n-2*k)/n degrees. So in 6 points, the only solution is k = 1, so the angle is 120 degrees. In 7 point case, k could be 1, 2 or 3, when k = 1 the angle is 900/7 degrees; when k = 2 the angle is 540/7 degrees; when k = 3 the angle is 180/7 degrees
