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In geometry, a line segment is a part of a line that is bounded by two distinct end points, and contains every point on the line between its end points. A closed line segment includes both endpoints, while an open line segment excludes both endpoints; a half-open line segment includes exactly one of the endpoints. Examples of line segments include the sides of a triangle or square. More generally, when both of the segment's end points are vertices of a polygon or polyhedron, the line segment is either an edge (of that polygon or polyhedron) if they are adjacent vertices, or otherwise a diagonal. When the end points both lie on a curve such as a circle, a line segment is called a chord (of that curve). ==In real or complex vector spaces== If ''V'' is a vector space over or , and ''L'' is a subset of ''V'', then ''L'' is a line segment if ''L'' can be parameterized as : for some vectors , in which case the vectors u and are called the end points of ''L''. Sometimes one needs to distinguish between "open" and "closed" line segments. Then one defines a closed line segment as above, and an open line segment as a subset ''L'' that can be parametrized as : for some vectors . Equivalently, a line segment is the convex hull of two points. Thus, the line segment can be expressed as a convex combination of the segment's two end points. In geometry, it is sometimes defined that a point ''B'' is between two other points ''A'' and ''C'', if the distance ''AB'' added to the distance ''BC'' is equal to the distance ''AC''. Thus in the line segment with endpoints and is the following collection of points: :. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「line segment」の詳細全文を読む スポンサード リンク
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