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

Learn Geometric constructions: circle-inscribed square Geometric constructions: circle-inscribed equilateral triangle Geometric constructions: circle-inscribed regular hexagon

Learn the relationship between the radius, diameter, and circumference of a circle.

The standard form equation of a circle contains the squares of two binomials. Sometimes, we'll be asked to determine the center or radius of a circle represented by an equation in which the squares of the …

Review the standard and expanded forms of circle equations, and solve problems concerning them.

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. Created by Sal Khan and Monterey Institute for Technology …

Discover how to measure angles, distances, and heights using trigonometric ratios and the unit circle. Learn how to use sine, cosine, and tangent to solve real-world problems involving triangles and …

What are unit circle trigonometry problems? The problems in this lesson involve circles and angle measures in radians, a unit for angle measure much like degrees.

Learn the basics of circles with Khan Academy's interactive lessons and exercises designed to enhance your understanding of geometry concepts.

What is the unit circle definition of the trigonometric functions? The unit circle definition allows us to extend the domain of sine and cosine to all real numbers.