Videos and lessons with examples and solutions to help High School students understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle.

Understanding the definition and motivation for radians and the relationship between radians and degrees.

Find out what a radian is and how to convert between degrees and radians.

Earthlings say that there are 360 degrees in a circle. Martians would say that there are 670 degrees in a circle. Mathematicians say that there are 2*pi radians in a circle. This video explains what these are (and why they are called "radians").

What is Radian Measure?
How to convert from degrees to radian?
How to convert from radian to degrees?
How to evaluate trig function values in radian measure?

Measuring Angles: Degrees and Radians, Part 1
Are you confused about radians yet? Maybe these videos will clear up a thing or two for you.

Measuring Angles: Degrees and Radians, Part 2
Here's the second part of our explanation of radian angle measures.

Measuring Angles: Degrees and Radians, Part 3
In this final video on radian angle measures, we convert between degrees and radians and vice versa.

Wrapping the Number Line around the Unit Circle
The standard introduction to radian measure and unit circle trigonometry involves "wrapping" the real t number line around the unit circle. This Demonstration illustrates that wrapping. You can wrap either the positive or the negative values of t, and can choose between the number line having ticks at the integers or at multiples of π/2. The t number line is colored to enhance the visual understanding of which numbers end up where on the circle.

Convert the measure of an angle from radians to degrees or from degrees to radians.

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.