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Limits: The Basic Idea The intuitive meaning of $\lim\limits_{x \to c} f(x)$ For example: function $$f(x)= \begin{cases} x-1& \text{if x!=2} \\ 3& \text{if x=2} \end{cases}$$ The graph is: From the graph, in this function, $f(2)=2$. However, $\lim\limits_{x \to 2} f(x)$ is not 2. It is the only value where x is very very close to 2, not actually 2. From the graph, it is easy to claim that the value where x is close to 2 is 1 ($f(1.

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Basic Concept $x$: random variable. 其中 $x \in \mathbb{R} \quad or \quad x \in \mathbb{Z}$ $P(x=k)=a$: 对于$x=k$这个事件，他的概率为$a$。需要注意，任何事件的概率均大于等于0且小于等于一。 举个例子，x:

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Basic Concept 与discrets probability distribution不同的是, continuous probability distribution是连续的. 前者的变量只能是整数, 而后者是整个实数域. 与

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Basic Law of conservation of mass (质量守恒定律) 化学反应论“个”算 化学方程式：反应物，生成物，微观粒子个数比（化学计量比，数量效应），聚集态，反应条件，化学反应

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Migration: the permanent or semi-permanent relocation of people from one place to another. (Voluntary migration) a movement made by choice. • Push factors- the factor that lets people move out • Pull Factors- lets people move in Intervening obstacles: barriers that make reaching their desired destination more difficult (economic, social, political, or environmental) Urban Areas: Migrants traveling long distances usually settle in large urban areas. This is mainly because migrants

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Crude birth rate (CBR): the number of live births per year for each 1,000 people. Total fertility rate (TFR): the average number of children who would be born per woman of that group in a country, assuming every woman lived through her childbearing years. Anti-natalist policies: programs to decrease the number of births. Pro-natalist policies: programs designed to increase the fertility rate. Life expectancy (What’

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Midlatitudes: the regions between 30° N and 60° N, and between 30° S and 60° S. Low Lying Areas: place at or near sea level Fresh Water: People need fresh water to drink, irrigation, transport, and provide food. Arithmetic population density: dividing a region’s population by its total area. Physiological population density: dividing population by

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Patterns: The general arrangement of things being studied. Processes: The repeated sequences of events, that create patterns. Scale: the ratio between the size of things in the real world and the size of those same things on the map. Cartographic scale: the way the map communicates the ratio of its size to the size of what it represents: Geographic scale (relative scale): the amount of territory that the map represents.

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Physical geography: the study of spatial characteristics of various elements of the physical environment. Human geography: the study of the spatial characteristics of humans and human activities. Toponym: the name of a place Site: the characteristics at the immediate location—for example, the soil type, climate, labor force, and human structures. Situation: the location of a place relative to its