You know, cosine is adjacent over hypotenuse.

你们知道 cos邻边除以斜边。

That's the cosine of 30 degrees.

这cos30度。

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的因 theta 的余弦。

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。

What's the cosine of 30 degrees?

cos30度多少？

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。

98 times the cosine of 30 degrees newtons.

98乘以 cos 30度牛顿。

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

因此 两者相等。

Because cosine of 0 right now is 1.

因此 两者相等。

So this is equal to cosine of the angle.

cosθ等于邻边/斜边。

Here I'm only showing cosines for simplicity.

在这里， 为了简单起见，我只显示余弦。

The  force of gravity perpendicular equals mass times gravitational field strength times the cosine of  the incline angle.

垂直重力等于质量乘以重力场强度乘以倾斜角的余弦。

How is knowing cosines gonna help you with your backstroke?

学会余弦对仰泳有什么帮助？

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

因此， theta 的余弦等于（球的位置）除以它的（振幅）。

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。

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。

The cosine of zero is 1.

零的余弦 1。

In other words, the ball’s position is equal to (the amplitude), times (the cosine of the angle).

换句话说， 球的位置等于（振幅）乘以（角度的余弦值）。

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的延伸。

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

所以theta的答案等于位置 球除以幅度。