本教程还假设您了解地图的一些关键特性：距离、坐标和比例尺。

The tutorial also assumes you know some key features of a map: distance, coordinates, and scale.

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坐标是数字值，代表角度或直线距离。

Coordinates are numeric values, representing either angles or linear distances.

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X 坐标：X 坐标是某一个点距离原点的水平距离。

X coordinates: The X coordinate is a point's horizontal distance from the origin.

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That was Cartesian space. When I plot r as a distance out from the nucleus that is sort of our simple-minded planetary model. Now let's look at energy.

笛卡尔坐标系，当我用r表示,离原子核的距离时，那只是我们头脑中简单的,类似行星的模型，现在我们看一下能量问题。

麻省理工公开课 - 固态化学导论课程节选