An annulus of a circle is defined and then a proof like problem is posed involving area and radius of circles.

Solve two challenging problems that apply properties of tangents to find the radius of a circle with a tangent.

This reference tool explores the radius of a circle. Provides definitions, solved examples, and practice questions with answers.

WebMath offers a java applet that allows you to input information about a circle, in one of four forms, and gives you the graph of the circle.

In this activity, students bisect the angles of a triangle and find the incenter of the triangle. They find the distance from the incenter to the side of the triangle and use it as radius. With the incenter as the center, they inscribe a...

[Free Registration/Login Required] This flipchart reviews basic geometric forms in nature and real objects. Students are then given opportunities to find the area of circle and parts of a circle, given the radius and/or diameter of the...

In this activity, students investigate the relationship between the coordinates of a point on the circle, radius of a circle, and the values in the equation of the circle.

Explore the relationship between the center and radius of a circle and the equation of the circle. Collect data and determine regression equations related to various combinations of data, and use the regression equations to make...

In this activity, students will explore the relationship among the location of the center of the circle, the radius of a circle, and the equation of a circle in a plane. They will also investigate the relationship between the points...

[Free Registration/Login may be required to access all resource tools.] In this lesson students find the area of a sector or segment. Students examine guided notes, review guided practice, watch instructional videos and attempt practice...

This video lesson demonstrates how to work backward and use the volume of a cylinder to find an unknown value such as the radius or height. Students can check their understanding with an assessment. [4:41]

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?

Get independent practice working with finding the circumference, area and radius of circles. Each incorrect response gets a text box explanation and another try. Correct responses are confirmed.

The students will identify parts of the circle including center, radius, diameter, chord, and arc. This lesson plan was created by exemplary Alabama Math Teachers through the AMSTI project.

Suppose we are given a circle of radius r. The goal of this task is to construct an equilateral triangle whose three vertices lie on the circle. Aligns with G-CO.D.13.

In this activity, students use the distance of the circumcenter of a triangle to each vertex of the triangle as the radius and draw a circle using the circumcenter as the center.

Understand how we can calculate the radius of a circle of confusion

In this video, students visit a small-town festival that features the world's largest stainless steel skillet. In addition to a question about scaling recipes, they also are asked how increasing or decreasing the radius of a circle...

This interactive exercise focuses on working with the radius of various circles to find the circumference and area as well as challenging you to find the distance a square wheel travels around the track.

Practice finding the radius and diameter of a circle using both vocabulary and visuals. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.

[Free Registration/Login may be required to access all resource tools.] In this lesson students find the circumference of a circle given the radius or the diameter. Students examine guided notes, review guided practice, watch...

[Free Registration/Login may be required to access all resource tools.] In this lesson students find the circumference of a circle given its diameter or radius. Students examine guided notes, review guided practice, watch instructional...

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.

Use the formula given for the area of a circle and a square to solve this challenge. This one page website has the solution available for you.