polar axis

American  

noun

Mathematics.

1. the fixed line, usually horizontal, from which the angle made by the radius vector is measured in a polar coordinate system.

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polar axis British  

noun

1. the fixed line in a system of polar coordinates from which the polar angle, θ, is measured anticlockwise

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Etymology

Origin of polar axis

First recorded in 1890–95

Example Sentences

To test for symmetry about the polar axis, first try replacing θ with −θ.

From Textbooks • Mar. 30, 2016

This demonstrates that the graph is symmetric with respect to the polar axis.

From Textbooks • Mar. 30, 2016

We can also define a conic in terms of a fixed point, the focus at the pole, and a line, the directrix, which is perpendicular to the polar axis.

From Textbooks • Feb. 13, 2015

Perhaps the graph does cross the polar axis, but not at the pole.

From Textbooks • Feb. 13, 2015

In considering the movements of our planet, we shall see that no great changes in the position of the polar axis can have taken place.

From Outlines of the Earth's History A Popular Study in Physiography by Shaler, Nathaniel Southgate