1 =π/ 180， 1rad= 180 /π.

A week is 360 degrees, which is also 2π radians, which means 360 = 2π.

In mathematics and physics, radian is the unit of measurement of angle. It is a unit derived from the international system of units, abbreviated as rad. Definition: an arc whose arc length is equal to the radius and whose central angle is 1 radian.

Radian:

The angle is expressed in radians, and the angle expressed in radians has no unit, so it is a real number. For example, 30 in Sin30 is 30 in real number (positive integer in real number, of course), and 30 in SIN 30 is to divide a circle into 360 equal parts and take out 30 parts.

We know that the angle SIN 30 = 1/2 and the radian SIN 30 =-0.9 1625.

1 =2π/360=π/ 180。

The significance of introducing the concept of radian is that it takes trigonometric functions with angles and other functions as independent variables to study their domain, maximum and minimum values and so on.