First of all, it's clear from the Pythagoras' theorem that a is the square root of ^2 + ^2.

首先,根据毕达哥拉斯定理,勾股定理在西方被称为"毕达哥拉斯定理"

耶鲁公开课 - 基础物理课程节选

If you give me a pair of numbers, Ax and Ay, that's as good as giving me this arrow, because I can find the length of the arrow by Pythagoras' theorem.

如果给我一组数字,Ax 和 Ay,就相当于给了我这个箭头示意图,因为我可以利用毕达哥拉斯定理定理求出模长

耶鲁公开课 - 基础物理课程节选

With research continuing into this strand of ancient history, it remains to be seen whether Pythagoras's theorem will come to bear the name of an old Babylonian scribe instead.

CNN: Pythagoras, a math genius? Not by Babylonian standards