CK-12 Foundation
Ck 12: Geometry: Surface Area and Volume of Cones
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to calculate the surface area and volume of a cone.
Mathigon
Mathigon: Geometry: Circle and Pi: Introduction
This lesson focuses on the characteristics of a circle including similarity, radius, circumference, and Pi. It provides formulas to determine the area of a circle, calculating Pi, and learning exercises throughout.
CK-12 Foundation
Ck 12: Geometry: Circumference and Arc Length Study Guide
This study guide on circumference and arc length covers key vocabulary, the parts of a circle, and formulas for circumference, area, and arc length. It is available for download with free registration.
Thinkport Education
Math by Design: Circumference and Area of a Circle [Pdf]
Students will discover how to estimate and measure the circumference and area of a circle.
Cool Math
Coolmath: Precalculus Basic Formulas to Know
This CoolMath resource provides an introduction to some Precalculus formulas.
Math Open Reference
Math Open Reference: Parts of a Circle
Learn about parts of a circle with this pictorial index. Click on the diagrams for more information. Includes links to related topics.
National Council of Teachers of Mathematics
Nctm: Illuminations: Power of a Point
Use this tool to investigate what happens when point P is moved to various points within, on, and outside the circle. Can you identify any relationships among the segments and radius?
Math Open Reference
Math Open Reference: Circumference (Perimeter) of a Circle
Learn about the circumference of a circle with this helpful reference tool. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Math Open Reference
Math Open Reference: Radius of a Circle
Learn about the radius of a circle with this useful reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Cuemath
Cuemath: Radius
This reference tool explores the radius of a circle. Provides definitions, solved examples, and practice questions with answers.
Math Open Reference
Math Open Reference: Diameter
A complete reference guide to diameters. It provides definitions, examples, and interactive activities that enhance further explanation. Includes links to related topics.
Math Open Reference
Math Open Reference: Area Enclosed by a Circle
A complete reference guide to the area enclosed by a circle. It provides definitions, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
CK-12 Foundation
Ck 12: Interactive Geometry: 8.2 Area and Circumference of Circles
A deep dive into the area and circumference of circles.
Quia
Ixl Learning: Area of Circles
Brush up on your math skills relating to the area of circles then try some practice problems to test your understanding.
Wolfram Research
Wolfram Math World: Apothem
MathWorld offers a definition of the apothem of a circle as well as an illustration is provided on this page. An equation is also provided to calculate the apothem of a circle given the radius and the sagitta.
Wolfram Research
Wolfram Math World: Radius
This math site from MathWorld.com defines radius in terms of both a circle and a sphere. The site includes a diagram and links to related topics.
Wolfram Research
Wolfram Math World: Circle
This site from Mathworld provides a wealth of information about circles is presented. The information ranges from the basics--radius, circumference, etc.--to advanced concepts--equations in polar and pedal coordinates, etc.
Wolfram Research
Wolfram Math World: Circumference
This site provides the formula for circumference. Links are provided.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Conical Sections
This question and answer site deals with finding the diameter of one end of a frustum of a cone when you know the diameter and angle of the end as well as the length of the cone.
Math Words
Math Words: Frustum of a Cone or Pyramid
This site defines a frustum and has links to related topics. The site offers the formula for the lateral area, volume, and total surface area of frustum of a cone.
Vernet -Virtual Education Resources Network
Salon Hogar: Referencia Rapida De Formulas Geometricas
This site provides the user with a useful reference to different geometric forms, their elements, formulas, and areas. Entirely in Spanish.
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Circunferencia Y Circulo: Longitudes Y Areas
Reinforce your knowledge of the circumference and the area of a circle with these activities. [Requires Java.]
Learning Wave Communications
Learning Wave: Geometry, Section 2
Geometry concepts are briefly discussed at this site, including volume of a cylinder, parallelograms, circles, trapezoids, and triangles. Sample problems and applications are included for practice.