radian Trig.
(ˈreɪdɪən)
[f. radi-us + -an.]
(See quot. 1879.)
| 1879 Thomson & Tait Nat. Phil. I. i. §41 The usual unit angle is..that which subtends at the centre of a circle an arc whose length is equal to the radius;..for brevity we shall call this angle a radian. 1881 Halsted Mensuration 24 The number which expresses any angle in radians also expresses its intercepted arc in terms of the radius. |