Radian
What is radian?
The radian is the standard unit of angular measure. An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle. One radian is equal to 57.3 degrees (when the arc length is equal to the radius).
Definition
Move Point C, try to find the relationship between radians and degrees
The relationship between radians and degrees
In a half circle there are π radians, which is also 180°So: π radians =180°
So: 1 radian=180°/π =57.2958...° (approximately)
To go from radians to degrees: multiply by 180, divide by π
To go from degrees to radians: multiply by π, divide by 180
What's the radian for 30 degrees?
How many degree is 2π?