The central angle of an arc whose arc length is equal to the radius of a circle is 1 radian. According to the definition, the radian of a week is 2πr/r=2π, and the 360-degree angle is 2π radian, so the radian of 1 is about 57.3, that is, 57 17' 44.806'', and 1 is π/ 188.