octant

American  

[ok-tuhnt] / ˈɒk tənt /

noun

1. the eighth part of a circle.

2. Mathematics. any of the eight parts into which three mutually perpendicular planes divide space.

3. an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.

4. the position of one heavenly body when 45° distant from another.

5. Astronomy. Octant, the constellation Octans.

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octant British  

/ ˈɒktənt /

noun

1. maths

   1. any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space

   2. an eighth part of a circle

2. astronomy the position of a celestial body when it is at an angular distance of 45° from another body

3. an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°

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Other Word Forms

• octantal adjective

Etymology

Origin of octant

First recorded in 1680–90; from Latin octant- (stem of octāns ); Octans

Example Sentences

Find the volume of the solid situated in the first octant and determined by the planes z = 2, z = 0, x + y = 1, x = 0, and y = 0.

From Textbooks • Mar. 30, 2016

The solid E bounded by z = 1 − x2 and situated in the first octant is given in the following figure.

From Textbooks • Mar. 30, 2016

As before, we use the first octant x ≥ 0, y ≥ 0, and z ≥ 0 and then multiply the result by 8.

From Textbooks • Mar. 30, 2016

Find the maximum volume of a rectangular box with three faces in the coordinate planes and a vertex in the first octant on the plane x + y + z = 1.

From Textbooks • Mar. 30, 2016

It consists of a frame in the form of an octant having a graduated scale upon its arc, and an index arm, or alidade pivoted at its apex.

From The Gutenberg Webster's Unabridged Dictionary Section P and Q by Project Gutenberg