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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Circular sector ： ウィキペディア英語版 Circular sector A circular sector or circle sector (symbol: ⌔), is the portion of a disk enclosed by two radii and an arc, where the smaller area is known as the minor sector and the larger being the major sector. In the diagram, θ is the central angle in radians, $r$ the radius of the circle, and $L$ is the arc length of the minor sector. A sector with the central angle of 180° is called a half-disk and is bounded by a diameter and a semicircle. Sectors with other central angles are sometimes given special names, these include quadrants (90°), sextants (60°) and octants (45°). The angle formed by connecting the endpoints of the arc to any point on the circumference that is not in the sector is equal to half the central angle. == Area == The total area of a circle is $\backslash pi\; r^2$. The area of the sector can be obtained by multiplying the circle's area by the ratio of the angle and $2\; \backslash pi$ (because the area of the sector is proportional to the angle, and $2\; \backslash pi$ is the angle for the whole circle, in radians): :$A\; =$ \pi r^2 \cdot \frac = \frac The area of a sector in terms of $L$ can be obtained by multiplying the total area $\backslash pi\; r^2$by the ratio of $L$ to the total perimeter $2\backslash pi\; r$. :$A\; =$ \pi r^2 \cdot \frac = \frac Another approach is to consider this area as the result of the following integral : :$A\; =$ \int_0^\theta\int_0^r dS=\int_0^\theta\int_0^r \tilde d\tilde d\tilde = \int_0^\theta \frac r^2 d\tilde = \frac Converting the central angle into degrees gives :$A\; =\; \backslash pi\; r^2\; \backslash cdot\; \backslash frac$ 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「Circular sector」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.