Learn about circles, their properties, equations, and applications through interactive lessons and exercises on Khan Academy.

Explore geometry concepts related to circles, including properties, formulas, and applications, through engaging lessons and exercises on Khan Academy.

Note: All angle measures in this lesson are in degrees. To learn more about radians, check out the Unit circle trigonometry lesson.

Practice your understanding of the unit circle definition of sine and cosine.

The problems in this lesson involve circles and angle measures in radians, a unit for angle measure much like degrees. We can use radian measures to calculate arc lengths and sector areas, and we …

Find the area of a circle given its radius, diameter, or circumference.

Learn about the unit circle and radians with interactive lessons and practice problems on Khan Academy, a free online learning platform.

Khan Academy ... Khan Academy

Oops. Something went wrong. Please try again. Uh oh, it looks like we ran into an error. You need to refresh. If this problem persists, tell us.

The area of a circle is pi times the radius squared (A = π r²). Learn how to use this formula to find the area of a circle when given the diameter.