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Circle and Pi: online activities, games, and tutorials

This is a hand-picked list of online tools, activities, games, and worksheets about the parts of a circle, area of a circle, and Pi.

Circle / Pi

Circle Worksheets
Customizable worksheets for the area/circumference/radius of a circle.
/worksheets/circle.php

Area of a Circle, Formula & Illustrated Lesson
The interactive tool shows you the area of the circle as the radius increases. The page also includes a short quiz.
https://www.mathwarehouse.com/geometry/circle/area-of-circle.php

Circle Tool
An applet that allows you to investigate how the area and circumference of a circle compare to its radius and diameter in the Intro and Investigation sections and then hone your skills in the Problems section. You can drag the radius to various lengths, and the click the "Add to Table" button to record the data in the table. You can also examine the ratios of any two measures, and make a graph of the data.
illuminations.nctm.org/ActivityDetail.aspx?ID=116

Radius, Diameter, and Circumference
A simple lesson with an interactive quiz about radius, diameter, and circumference of a circle.
www.mathgoodies.com/lessons/vol2/circumference.html

The Area of a Circle as a Limit
An animation that illustrates how the area of a circle is a limit of the sum of the areas of interior triangles as the number of triangles goes to infinity. This is the idea I explain in this book (Math Mammoth Geometry 2).
www.learnerstv.com/animation/animation.php?ani=96&cat=physics

Area of Circle
An activity where you measure a circle and the resulting figure when you cut it into wedges and tape them together to form a crude parallelogram.
www.learner.org/courses/learningmath/measurement/session7/part_b

Key to Geometry Workbooks

Here is a non-intimidating way to prepare students for formal geometry. Key to Geometry workbooks introduce students to a wide range of geometric discoveries as they do step-by-step constructions. Using only a pencil, compass, and straightedge, students begin by drawing lines, bisecting angles, and reproducing segments. Later they do sophisticated constructions involving over a dozen steps-and are prompted to form their own generalizations. When they finish, students will have been introduced to 134 geometric terms and will be ready to tackle formal proofs.

=> Learn more

Rolling circle illustrating Pi
This is a short animation where a circle with diameter 1 rolls on a number line one complete roll. Of course having rolled once around its circumference, it now lands at 3.14 or Pi.
https://i.imgur.com/dsCw0.gif

 Dr. Math Introduces Geometry: Learning Geometry is Easy! Just ask Dr. Math! A supplement to middle school geometry, Dr. Math Introduces Geometry has a light tone, clear layout, and humorous cartoons by Jessica Wolk-Stanley. The best part is that the explanations to math questions are accurate and clear. You'll find answers to dozens of real questions from students who needed help understanding the basic concepts of geometry. This book covers angles, triangles, quadrilaterals, area, perimeter, Pi, circle parts, polyhedra, surface area, volume, nets, congruent transformations, and symmetry. Price ~\$12 new, ~\$1-6 used.

Geometry worksheets at AGMath.com
Hundreds of free PDF worksheets for high school geometry topics, including geometric constructions, triangle congruence, circle, area, the Pythagorean Theorem, solid geometry, and similarity. The worksheets are loosely based on the "Discovering Geometry" textbook by Michael Serra. Compiled by math teacher Jason Batterson.
AGmath.com/1973.html

Amazing History of Pi
A short and simple introduction to the history of pi.
ualr.edu/lasmoller/pi.html

Approximating Pi
How did Archimedes find the approximate value of pi? This interactive tool illustrates Archimedes' basic approach with inscribed or circumscribed polygons.
www.pbs.org/wgbh/nova/archimedes/pi.html

Pi Day Activities & Links
Two pi-related activities to do at home, plus a lot of fun links about pi. Originally meant for Pi Day (celebrated 3/14 each year).
www.exploratorium.edu/pi/pi_activities

Visualization of the first 4 million digits of Pi
This online visualization represents the first 4,000,000 decimals of Pi within a single image. Each unique digit of Pi corresponds to a specific color, and is rendered as a 1x1 pixel dot. You can also search for the first occurrences of any specific decimal combination.
two-n.com/pi

5 Trillion Digits of Pi
As of August 2010, the world record for computing digits of pi was 5 trillion digits. This will keep changing, of course.
www.numberworld.org/digits/Pi

Books

Math Mammoth Geometry 2
A textbook/workbook together for grades 6-7, written by the owner of this site. It continues the study of goemetry after Math Mammoth Geometry 1, continually emphasizing conceptual understanding, besides calculation-type exercises. Price: \$5.80 download.
www.mathmammoth.com/geometry_2.php

Geometry: A Guided Inquiry
An excellent choice for high school geometry. I've written an in-depth review of this book and of its supplement Home Study Companion - Geometry, latter by David Chandler.

Harold Jacobs Geometry
A popular choice for geometry among homeschoolers, and well written. Please read my review.

Dr. Math Presents More Geometry
An inexpensive companion to any high school geometry course with excellent explanations. Read my review.

Key to Geometry Workbooks

Here is a non-intimidating way to prepare students for formal geometry. Key to Geometry workbooks introduce students to a wide range of geometric discoveries as they do step-by-step constructions. Using only a pencil, compass, and straightedge, students begin by drawing lines, bisecting angles, and reproducing segments. Later they do sophisticated constructions involving over a dozen steps-and are prompted to form their own generalizations. When they finish, students will have been introduced to 134 geometric terms and will be ready to tackle formal proofs.

=> Learn more