Definition:Polar Coordinates/Polar Axis
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Polar coordinates are a technique for unique identification of points on the plane.
Let $O$ be the pole of the polar coordinate plane.
A ray is drawn from $O$, usually to the right, and referred to as the polar axis.
Also known as
Some sources refer to this as the initial line
Some use the term initial vector.
The plural of axis is axes, which is pronounced ax-eez not ax-iz.
- 1933: D.M.Y. Sommerville: Analytical Conics (3rd ed.) ... (previous) ... (next): Chapter $\text I$. Coordinates: $2$. Coordinates
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): initial line