So both are useful, and in assignment 7 I'll give you a simple problem so that you can apply the perpendicular axis theorem.
俩定理都有用，第七次作业中我会，给你们简单的问题，用到垂直轴定理。
When a surface is perpendicular to the rays, their intensity is at its maximum.
当表面与射线垂直时，射线的强度最大。
The researchers found that if they stretched out the substance in a second direction perpendicular to the first, it could then be stretched in any direction without harm.
研究人员发现，如果向着第一次拉伸的垂直方向拉扯，它仍然能够向着任何方向毫无损害地任意伸展。
Let's break the name down. The "normal" is a vector perpendicular to a surface, which we can use to calculate lighting.
首先我们从名字上开始分析，所谓“法线”指的是垂直于平面的向量，我们使用这个来计算光照。
OK, so now if we have a dot product that's zero, that tells us that these two guys are perpendicular.
所以我们现在有了一个点积为，这告诉我们两者是垂直的。
So what she's going to do is start loading up the electrons, and you see this wand here move slowly, and it takes a while to do it, start become perpendicular.
所以她将要加载电子，你们看到这个棒慢慢地移动，这个需要一段时间，开始变得垂直了。
However, a vertical line sitting perpendicular to the top and bottom of the canvas has more of a tendency to convey a sense of height.
然而，与画布顶端和底端垂直的竖线往往更适于传递高度之感。
The directional derivative in a direction that's perpendicular to the gradient is basically zero.
垂直于梯度的方向上,方向导数为零。
Vector dS is a vector which points perpendicular to the surface and whose length corresponds to the surface element.
向量dS与曲面垂直,并且它的长度与面积元素有关。
A severe facade rose above this door; a wall, perpendicular to the facade, almost touched the door, and flanked it with an abrupt right angle.
大门的上方便是那房屋的正面，气象庄严，一道和房屋正面垂直的墙紧靠在大门旁边，构成一个生硬的直角。
A surface having parabolic sections parallel to a single coordinate axis and elliptic sections perpendicular to that axis.
抛物面一种有与单坐标轴平行的抛物截面和与该轴垂直的椭圆截面的平面。
Or add transparent graphics with computed transparencies perpendicular to the Earth plane to create a more realistic layered effect for all viewing angles.
或者，添加与地平面垂直的、计算出透明度的透明图形，创建针对所有视角的更真实的分层效果。
Actually, they have a vector field is still pointing perpendicular to the level curves that we have seen, just to remind you.
实际上，向量场，还是垂直于水平线，就像之前看到的那样，我只是想提醒一下大家。
A rare galaxy type, polar ring galaxies have a substantial population of stars, gas, and dust orbiting in rings nearly perpendicular to the plane of the galactic disk.
极环星系是种稀有的星系类型，它们有着几乎和银盘平面垂直，呈环形公转的大量的恒星、气体和星尘。
I mean we'd seen in last time, but the gradient is perpendicular to the level and points towards higher values of a function.
我的意思是，上一次我们讨论过了，这个梯度是垂直于等高线，并且是指向方程增长的方向的。
一个与半径垂直的矢量。
On the inside lane, less than a yard outside your window, stands a wall of treeless rock that climbs upward in a nearly perpendicular line.
在内车道，距离你的车窗不到一码的距离，就是没有杂草的是山岩，向上磊成几近垂直路沿。
Consider a ball that is spinning about an axis perpendicular to the flow of air across it (see left).
观察一个旋转轴与空气流动方向垂直的足球(见上图)。
The 90-degree angles formed by perpendicular lines have a tendency to create visual rigidity, which in turn suggests permanence and reliability.
互相垂直的线构成的90度直角往往能创造视觉刚性，进而联想到永久与可靠。
In a vacuum they all travel at the speed of light; they are all composed of electric and magnetic vectors which are perpendicular to each other; they are all quantized as photons, and so on.
在真空中，它们都以光速前进；它们都由彼此垂直的电磁矢量构成；它们都可以用光子来量化，等等。
On a snowboard, the torso's natural position is more or less perpendicular to the direction of motion.
在单板上，人的躯干大致和运动方向垂直，十分自然。
The first one will be above and below the bond axis is where we'll see the electron density, and the second will be perpendicular to that, so it will be a density in front of and behind the bond axis.
第一个是在键轴之上和之下，我们可以看到电子密度，另外一个垂直于它，所以在键轴之前和之后有电子密度。
And we know how to find a normal vector to the level set, namely the gradient vector is always perpendicular to the level set.
我们是知道如何去求水平集的法向量的，也就是垂直于水平集的法向量。
Near the southern tip of south America, a trio of volcanoes lines up perpendicular to the Andes Mountains.
在南美洲的南端，三座火山垂直于安第斯山脉排列成行。
Well, it means that OP and a are perpendicular.
就像前面说过的，这就是说op和A互相垂直。
Why is that? Well, let's say that we know how to find a vector that's perpendicular to our plane.
为啥呢？呃，就是说，我们知道，怎么画垂直于这个平面的向量。
That is a property of the circle that the radial direction is perpendicular to the circle. Actually, let me complete this picture.
这不过是圆的性质——径向垂直于圆，我来画完这张图吧。
That is a property of the circle that the radial direction is perpendicular to the circle. Actually, let me complete this picture.
这不过是圆的性质——径向垂直于圆，我来画完这张图吧。
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