You know, cosine is adjacent over hypotenuse.

你们知道 cos是邻边除以斜边。

That's the cosine of 30 degrees.

这是cos30。

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素正是 theta 的余弦。

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

但让我们再来说说正弦、余弦和对数函数。

What's the cosine of 30 degrees?

cos30是？

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

还要完成上万笔计算处理余弦，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。

And the cosine of 90 degrees is zero.

90 的余弦为零。

Here I'm only showing cosines for simplicity.

在这里， 为了简单起见，我只显示余弦。

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

但是，让我们使用 E dA 余弦西塔来代替点积。

How is knowing cosines gonna help you with your backstroke?

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）。

The cosine of zero is 1.

零的余弦是 1。

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

我根本不知道正弦和余弦是什么意思。

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

所以余弦定律是勾股定理对任意角的延伸。

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（角的余弦值）。

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。