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Khan Academy

Khan Academy: Radius and Diameter

For Students 7th Standards
Practice problems finding radius and diameter of a circle.
Interactive
National Council of Teachers of Mathematics

Nctm: Illuminations: Circle Area

For Students 3rd - 8th Standards
Explore what the relationship the radius has to the area of a circle. Click the instructions to learn how to use this interactive resource and select"Exploration" for more ideas.
Activity
Texas Instruments

Texas Instruments: Match the Graph (Circles)

For Teachers 9th - 10th
Students will learn about the equation for a circle by using a Study Cards stack. Later, students will attempt to match the graph of a circle from a digital picture, using the form learned previously, and approximating the center and...
Activity
Texas Instruments

Texas Instruments: Circles in the Plane

For Teachers 9th - 10th
In this activity, students can use the Cabri Jr. application to explore circles in a plane. They will investigate the relationship between the equation of a circle, the length of its radius, and the coordinates of its center. [Requires...
Unit Plan
E-learning for Kids

E Learning for Kids: Math: World of Fish: Geometry

For Students 5th - 6th
Students will play an interactive game to identify the circumference, radius, center, and diameter of circles.
Activity
Math Open Reference

Math Open Reference: Circles

For Students 9th - 10th Standards
A complete reference guide to circles including parts, angles, and arcs. It provides definitions and interactive activities that enhance further explanation.
Unit Plan
CK-12 Foundation

Ck 12: Geometry: Circles in the Coordinate Plane

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to graph circles and find the standard equations of circles. Students examine guided notes, review guided practice, watch...
Interactive
Physics Classroom

The Physics Classroom: Circular & Satellite Motion: Uniform Circular Motion

For Students 9th - 10th
Manipulate variables while exploring principles and relationships related to moving in a circle at a constant speed. Students change the radius of the circle, the speed of the object, and the mass of the object and investigate the effect...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Gpe Explaining the Equation for a Circle

For Teachers 9th - 10th Standards
This problem examines equations defining different circles in the x-y plane. Students must use the Pythagorean Theorem to find equations whose solutions are points on the circle and explain why they work. Includes a GeoGebra worksheet...
Activity
Texas Instruments

Texas Instruments: Math Today Coming Clean About Showering Time

For Teachers 9th - 10th
In this activity using the USA TODAY Snapshot, "Coming clean about showering time," students will find the measures of central angles and arcs of a circle. They will use circumference, radius, concentric circles and degrees in a circle...
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McGraw Hill

Glencoe Mathematics: Online Study Tool: Self Check Quiz on Circles

For Students 9th - 10th Standards
The online assessment exhibits knowledge of advanced mathematical concepts in Trigonometry. The questions evaluate students on the topic of circles.
Handout
Math Is Fun

Math Is Fun: Definition of Circumference

For Students 3rd - 8th Standards
Definition of circumference. Click the "here's more" link to learn more about a circle; its radius and diameter, area, lines, slices and common sectors.
Unit Plan
Cuemath

Cuemath: Cone

For Students 9th - 10th Standards
Learn all about the basic properties of a cone. This lesson targets the formula, volume, parts, and shapes of a cone and has interesting solved examples and practice questions.
eBook
Mathigon

Mathigon: Geometry: Circle and Pi: Degrees and Radians

For Students 9th - 10th Standards
Rather than dividing a circle into some number of segments (like 360 degrees), mathematicians often prefer to measure angles using the circumference of a unit circle - a circle with radius 1. This way of measuring angles is called...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: F Tf.1 What Exactly Is a Radian?

For Teachers 9th - 10th Standards
For this task, students use a piece of string or another tool to measure the radius of the circle and then mark off the corresponding arc length on the unit circle as many times as they need to for 0, 1, 2, 3, 4, 5, and 6 radians. They...
Unit Plan
Texas Education Agency

Texas Gateway: Circular Motion & Gravitation: Rotation Angle & Angular Velocity

For Students 11th - 12th
By the end of this section, you will be able to define arc length, rotation angle, radius of curvature, and angular velocity; and to calculate the angular velocity of a car wheel spin.
Unit Plan
Cuemath

Cuemath: Diameter

For Students 6th - 8th
Understand the concept of diameter by learning the definition and symbols. Check-out the solved examples for better understanding and try your hand at solving a few interactive questions at the end of the page.
Article
Mocomi & Anibrain Digital Technologies

Mocomi: What Is Circle?

For Students 2nd - 8th
Discusses the radius, diameter, circumference, and area of a circle.
Interactive
Calculator Soup

Calculator Soup: Circle Calculator

For Students 9th - 10th Standards
Use this circle calculator to find the area, circumference, radius, or diameter of a circle. Given any one variable A, C, r or d of a circle you can calculate the other three unknowns.
Activity
CK-12 Foundation

Ck 12: Circles in the Coordinate Plane

For Students 9th - 10th
[Free Registration/Login Required] Students will move points on a circle to explore standard equations when given the radius and center. Click challenge me to answer practice problems and click learn more to watch a video.
Activity
Texas A&M University

Wtamu Virtual Math Lab: College Algebra: Circles

For Students 9th - 10th Standards
Use this tutorial to learn about the standard-form equation for a circle. Several step-by-step solutions and examples help you understand the part of the circle and how they relate to the equation.
Activity
CK-12 Foundation

Ck 12: Circles in the Coordinate Plane: Watering the Field

For Students 9th - 10th
[Free Registration/Login Required] Students can move points in a circle to determine the standard equation from the raidus and center. Click challenge me to answer practice questions and click learn more to watch a video.
Whiteboard
ClassFlow

Class Flow: Completing the Square Circles

For Teachers 9th - 10th Standards
[Free Registration/Login Required] This flipchart is a simple and basic flip chart showing how to find the center and radius of a circle that is in standard form as well as completing the square for equations of circles that are not in...
Study Guide
Oswego City School District

Regents Exam Prep Center: Area of Polygons and Circles

For Teachers 9th - 10th Standards
A lesson focusing on the area of polygons and the circumference of circles. Engaging, interactive practice worksheet, lesson plan, and related classroom activity complete this lesson.