Radians

Definition

Radians are a unit of angular measure in which the angle is defined by the ratio of the length of an arc to its radius. One radian is the angle subtended at the center of a circle by an arc whose length is equal to the radius.

5 Must Know Facts For Your Next Test

1. The circumference of a circle is 2π radians.
2. There are π radians in 180 degrees.
3. To convert from degrees to radians, multiply by π/180.
4. To convert from radians to degrees, multiply by 180/π.
5. Radians provide a direct relationship between linear and angular measurements.

Review Questions

• How many radians are there in a full circle?
• Convert 90 degrees to radians.
• What is the formula for converting radians to degrees?

Related terms

Degrees: A measure for angles where one full rotation equals 360 degrees.

Arc Length: The distance measured along the curved line forming part of the circumference of a circle.

Radius: The distance from the center of a circle to any point on its circumference.