State three measures that could be the side lengths of a right triangle. Justify your answer.
a. 9, 40, 41; 9^2 + 40^2 = 41^2
b. 3, 4, 7; 3^2 + 4^2 = 7^2
c. 12, 12, 15; 12^2 + 12^2 = 15^2
d 6, 8, 12; 6^2 + 8^2 = 12^2 ​