Divisibility of Elements of Pythagorean Triple by 7/Mistake

Source Work

 * The Dictionary
 * $7$
 * $7$

Mistake

 * If $a$, $b$ are the shorter sides of a Pythagorean triangle, then $7$ divides one of $a$, $b$, $a - b$ or $a - b$.

An obvious misprint for:
 * If $a$, $b$ are the shorter sides of a Pythagorean triangle, then $7$ divides one of $a$, $b$, $a - b$ or $a + b$.