A line (straight line) can be thought of as a connected set of infinitely many points. It extends infinitely far in two opposite directions. A line has infinite length, zero width, and zero height. Any two points on the line name it. The symbol ↔ written on top of two letters is used to denote that line. A line may also be named by one small letter

Contoh

Lines AB, Lines AC

lines

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A point is the most fundamental object in geometry. It is represented by a dot and named by a capital letter. A point represents position only; it has zero size (that is, zero length, zero width, and zero height)

contoh

Point Q, Point A

planes

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A plane may be considered as an infinite set of points forming a connected flat surface extending infinitely far in all directions. A plane has infinite length, infinite width, and zero height (or thickness). It is usually represented in drawings by a four‐sided figure. A single capital letter is used to denote a plane. The word plane is written with the letter so as not to be confused with a point (Figure 4)