Answer
Pythagorean Triple.
Work Step by Step
The Pythagorean Theorem states that for a right triangle, $a^{2} +b^{2} = c^{2}$. In order to figure out if these sides can be a Pythagorean Triple, we plug them into the Pythagorean Theorem:
$28^{2} + 45^{2} = 53^{2} \\\\ 2809=2809$
This is true, so it is a Pythagorean Triple.