the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
In the International System of Units, the derived unit of plane angular measure of angle equal to the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle. Symbol: rad
Origin: From radi(us) + -an
an arc of a circle which is equal to the radius, or the angle measured by such an arc
Origin: [From Radius.]
The radian is the standard unit of angular measure, used in many areas of mathematics. An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle, so one radian is just under 57.3 degrees. The unit was formerly an SI supplementary unit, but this category was abolished in 1995 and the radian is now considered an SI derived unit. The SI unit of solid angle measurement is the steradian. The radian is represented by the symbol "rad" or, more rarely, by the superscript c. For example, an angle of 1.2 radians would be written as "1.2 rad" or "1.2c".
Chambers 20th Century Dictionary
rā′di-an, n. the angle subtended at the centre of a circle by an arc equal to the radius.
The Standard Electrical Dictionary
The angle whose arc is equal in length to the radius; the unit angle.
The numerical value of radian in Chaldean Numerology is: 5
The numerical value of radian in Pythagorean Numerology is: 2
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