The points of this 3-by-3 grid are equally spaced horizontally and vertically. How many different sets of three points of this grid can be the three vertices of an isosceles triangle?
The number of different sets of three points of this 3-by-3 grid that can be the three vertices of an isosceles triangle is 8. The 8 sets of three points are: (1,1), (3,1), (3,3); (1,1), (3,1), (1,3); (1,1), (1,3), (3,3); (1,3), (3,1), (3,3); (1,1), (2,2), (3,1); (1,1), (2,2), (1,3); (2,2), (3,1), (1,3); (2,2), (3,1), (3,3).
