1.You know, cosine is adjacent over hypotenuse.

你们知道 cos邻边除以斜边。

2.That's the cosine of 30 degrees.

这cos30度。

3.So the factor by which the slice gets squished down in this direction is exactly cosine of theta.

因此，切片 在这个方向上被压扁因素 theta 余弦。

4.But let me go back to these sines, cosines and logarithms.

但让我们再来说说弦、余弦和对数函数。

5.What's the cosine of 30 degrees?

cos30度多少？

6.And compute over 10,000 calculations by cosine, square root and lately Analytic Geometry.

还要完成上万笔计算处余弦，平方根，最近还用起了解析几何。

7.98 times the cosine of 30 degrees newtons.

98以 cos 30度牛顿。

8.And that's why it's cosine of theta.

因此 两者相等。

9.Because cosine of 0 right now is 1.

因此 两者相等。

10.So this is equal to cosine of the angle.

cosθ等于邻边/斜边。

11.And the cosine of 90 degrees is zero.

90 度余弦为零。机翻

12.The cosine of zero is 1.

零余弦 1。机翻

13.However, let's use E dA cosine theta instead of the dot product.

但，让我们使用 E dA 余弦西塔来代替点积。机翻

14.As the value t increases, the inside of this cosine function increases more slowly.

随着 t 值增加，该余弦函数内部增加得更慢。机翻

15.To calculate a triangle's shading, we take the  cosine of the angle or theta between the two directions.

为了计算三角形阴影，我们取两个方向之间角度或 θ 余弦。机翻

16.How is knowing cosines gonna help you with your backstroke?

学会余弦对仰泳有什么帮助？

17.So, the cosine of theta is equal to the (ball’s position) divided by its (amplitude).

因此， theta 余弦等于（球位置）除以它（振幅）。机翻

18.I don't have the slightest idea what sine and cosine mean.

我根本不知道弦和余弦什么意思。机翻

19.It's all just trigonometry, connecting sides and angles through sines and cosines.

这三角学，上边 以及跨弦和余弦角度。

20.So, the law of cosines is an extension of the pythagorean theorem to the arbitrary angles...

所以余弦定律勾股定对任意角度延伸。