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

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

Let S1 and S2 be the solids situated in the first octant under the plane x + y + z = 2 and under the sphere x2 + y2 + z2 = 4, respectively.

From Textbooks • Mar. 30, 2016

Give a parameterization for the portion of cone x2 + y2 = z2 lying in the first octant.

From Textbooks • Mar. 30, 2016

We can use a similar method to visualizing a vector field in ℝ2 by choosing points in each octant.

From Textbooks • Mar. 30, 2016

It is the sextant or some member of the sextant family - such as the quadrant, octant, etc.

From Lectures in Navigation by Draper, Ernest Gallaudet