arcsec
Abbreviation with 2 meanings
| Stands for | Arcsecond |
|---|---|
| Meanings | 2 |
| Categories | Units & Measurements |
arcsec has two meanings. It stands for Arcsecond (math) or Arcsecant (inverse secant) (math).
Meanings of arcsec at a glance
| # | arcsec stands for | Context |
|---|---|---|
| 1 | Arcsecond | Units & Measurements › Math |
| 2 | Arcsecant (inverse secant) | Units & Measurements › Math |
1. Arcsecond
Units & Measurements · Math Abbreviations
One sixtieth of an arcminute, or 1/3,600 of a degree, written ″. It is the unit of stellar parallax, telescope resolution and atmospheric "seeing" in astronomy.
Example: Atmospheric seeing at the observatory averaged 0.6 arcsec last night.
A star one parsec away shows a parallax of exactly one arcsecond, which is how the parsec is defined. The Hubble Space Telescope resolves about 0.05 arcsec, and the Gaia mission measured star positions to microarcseconds. An arcsecond is roughly the width of a coin seen from several kilometers away.
2. Arcsecant (inverse secant)
Units & Measurements · Math Abbreviations
Gives the angle whose secant equals a given value; real outputs exist only for inputs of 1 or more, or −1 or less. It appears mainly in calculus integral tables.
Example: The integral of 1/(x sqrt(x² − 1)) is arcsec x + C for x > 1.
Also written sec⁻¹ or asec. Because secant is the reciprocal of cosine, arcsec x equals arccos(1/x), which is how calculators compute it. Textbooks differ in the output range they choose, so formulas involving arcsec should be checked against the book's convention.
Related abbreviations
More math abbreviations
- a.e. – Almost everywhere
- AAS – Angle-Angle-Side (congruence)
- abs – Absolute value
- arccos – Arccosine (inverse cosine)
- arcmin – Arcminute
- arcsin – Arcsine (inverse sine)
- arctan – Arctangent (inverse tangent)
- arg – Argument (of a complex number)
- ASA – Angle-Side-Angle (congruence)
- B – Billion
- BEDMAS – Brackets, Exponents, Division/Multiplication, Addition/Subtraction
- bn – Billion