CK-12 Foundation
Ck 12: Geometry: Properties of a Circle Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide reviews the terminology for circles (tangent, arcs, central angles) and the equation for a circle.
Cuemath
Cuemath: Circles
Explore everything about circles. Learn various parts of a circle like a diameter, radius, circumference, circles chord, tangent circles, major arc, segment, sector, and discover other interesting aspects of it. Try your hand at solving...
Texas Instruments
Texas Instruments: Angles Formed by Intersecting Chords, Secants, and Tangents
In this activity, students will investigate properties of angles and arcs formed when chords, secants, and tangents intersect and intercept arcs in a circle. They discover several important theorems concerning circles and arc sizes. They...
Johan Claeys
Math Abundance: The Circle: Basic Concepts
Goes over the equation of a circle, parametric equations of a circle, intersection of circle and line, tangent line in a point of a circle, etc.
Math2
Math2: Circles
This site has many useful formulas and examples relating to circles, including related definitions, circumference of a circle, area of a circle, length of a circular arc, area of a circular sector, equation of a circle in cartesian...
CK-12 Foundation
Ck 12: Geometry: Circles: Segments and Lengths Study Guide
This study guide on circles covers some vocabulary and theorems about segments and lengths. It is available for download with free registration.
Math Open Reference
Math Open Reference: Circles
A complete reference guide to circles including parts, angles, and arcs. It provides definitions and interactive activities that enhance further explanation.
Lawrence Hall of Science
The Math Page: Trigonometry
Concepts in Trigonometry are explained and illustrated here by a member of the math department at Borough of Manhattan Community College.