Khan Academy Static

Arc_length_degrees_

Think about the relationship between central angle and arc length. This tutorial uses degrees not radians.

Introduction_to_radians

Most people know that you can measure angles with degrees, but only exceptionally worldly people know that radians can be an exciting alternative. As you'll see, degrees are somewhat arbitrary.

Circle_basics

Make sure you're familiar with notation and key terms like radius, diameter, circumference, pi, tangent, secant, and major/minor arcs before you dive into the rest of the circles content.

Arc_measure

Arc measure is equal to the arc's central angle. We'll explore this fact and solve some problems related to it.

Properties_of_tangents

Explore, prove, and apply properties of circles that involve tangents.

Inscribed_shapes_problem_solving

Use properties of inscribed angles to prove properties of inscribed shapes, then apply these properties some fun problem solving!

Standard_equation_of_a_circle

Learn about the standard form to represent a circle with an equation. For example, the equation (x-1)^2+(y+2)^2=9 is a circle whose center is (1,-2) and radius is 3.

Arc_length_radians_

Think about the relationships between arc measures, central angles, and arc length in radians.

Inscribed_angles

We'll now dig a bit deeper in our understanding of circles by looking at inscribed angles and related properties.

Expanded_equation_of_a_circle

Learn how to analyze an equation of a circle that is not given in the standard form. For example, find the center of the circle whose equation is x^2+y^2+4x-5=0.

Area_of_inscribed_triangle

This more advanced (and very optional) tutorial is fun to look at for enrichment. It builds to figuring out the formula for the area of a triangle inscribed in a circle!

Sectors

Learn how to find the area of a sector.

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