arc

mathematics

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June 18, 2026

Quick Summary

In mathematics, an arc is a continuous portion of a curved line, such as a circle or ellipse. The length of this curved segment is known as the arclength.12

The term "arc" can also refer to the apparent path of celestial bodies. In geometry, an arc is a segment of a circle's circumference, measured in degrees. The word "arc" is also used in the context of inverse trigonometric functions, such as "arc sine".13

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geoid
The ancients
Knowing the length of an arc (l) and the size of the corresponding central angle (a) that it subtends, one can obtain the radius of the sphere from the simple proportion that length of arc to size of the great circle (or circumference, 2πR, in which R is Earth’s radius)…
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Knowing the length of an arc (l) and the size of the corresponding central angle (a) that it subtends, one can obtain the radius of the sphere from the simple proportion that length of arc to size of the great circle (or circumference, 2πR, in which R is Earth’s radius)…
Read More