Root 2 simply is the hypotenuse of a right triangle

而 √2 只两边长度为 1 的 直之斜边。

A right triangle is a two dimensional figure with three side, two of which are perpendicular.

直具有条边的二维图，其中两条垂直的。

And you should also see that this is a right triangle that I have set up over here.

这个平行于斜面 而这个垂直于斜面这个平行于斜面 而这个垂直于斜面。

Take four identical right triangles with side lengths a and b and hypotenuse length c.

取四个全等的直，两边别长 a 和 b，斜边长 c。

The most famous relation in geometry is the relation between the sides and the hypotenuse of a right triangle.

几何中最著名的关系直的边和斜边之间的关系。

According to the converse of the Pythagorean theorem, that has to make a right triangle, and, therefore, a square corner.

根据毕达哥拉斯的逆定理，这就可以成一个直，因此，便可成直。

Picture a right triangle where side A is the tree.

想象一个直， 其中 A 边。

Somehow, rhomboids and isosceles right triangles didn't seem so important.

不知道为什么 菱和等腰直似乎没有那么重要了。

Similar experiments show that all shapes other than acute triangles, including right triangles, will also wake up.

类似的实验表明， 除了锐之外的所有状，包括直， 也会被唤醒。

You've got Babylonian surveyors who have their own unique understanding of right triangles and rectangles, and they're using it.

你有巴比伦的测量员，他们对直和矩有自己独特的理解，并且他们正在使用它。

That states that the squares of the sides of a right triangle add up to the square of its hypotenuse.

这表明直各边的平方加起来等于其斜边的平方。

And if you'd really like to convince yourself, you could build a turntable with three square boxes of equal depth connected to each other around a right triangle.

如果你真的想说服自己，你可以建个转台，上面有个相同深度的正方盒子，它们靠一个直相连。

But how do we know that the theorem is true for every right triangle on a flat surface, not just the ones these mathematicians and surveyors knew about?

但我们怎么知道这个定理对平面上的每个直都成立，而不一些数学家和测量人员所推测的呢？

This proof divides one right triangle into two others and uses the principle that if the corresponding angles of two triangles are the same, the ratio of their sides is the same, too.

这种证明将一个直为两个部，利用了如下定理：如果两个对应的相同，那么它们的边的比例也相同的。

You see, about a thousand years before the Greek astronomers were looking at the night sky. You've got Babylonian surveyors who have their own unique understanding of right triangles and rectangles, and they're using it.

在希腊天文学家观察夜空的一千年以前，巴比伦的测量员对直和矩有他们自己独特的理解，他们还会使用它。

Trigonometry -- which we use to calculate the angles and sides of triangles -- is going to come up a lot in physics, because we'll be using right angle triangles all the time.

学——我们用来计算的度和边——在物理学中会经常出现，因为我们将一直使用直。

They all came up with elegant proofs for the famous Pythagorean theorem; the rule that says for a right triangle, the square of one side plus the square of the other side is equal to the square of the hypotenuse.

他们都对毕达哥拉斯定理（勾股定理）做出了精彩的证明；这个定理说，对于一个直，一边的平方加上另一边的平方等于斜边的平方。

They all came up with elegant proofs for the famous Pythagorean theorem, the rule that says for a right triangle, the square of one side plus the square of the other side is equal to the square of the hypotenuse.

他们都为著名的毕达哥拉斯定理提出了优雅的证明，这条规则说对于直，一侧的平方加上另一侧的平方等于斜边的平方。