Varsity Tutors
Varsity Tutors: Hotmath: Graphing Calculator Practice Problems: Geometry
Practice using your graphing calculator for geometry problems, including the use of the Pythagorean Theorem and the distance formula. If you get stumped or if you would like to check your work, then select the View Solution button, which...
PBS
Pbs Learning Media: Formulas: Targeted Math Instruction
At the end of this lesson plan about formulas, students will be able to identify and apply the correct formula for a given situation, solve for any unknown component of the formulas for perimeter, circumference, and area of regular and...
Khan Academy
Khan Academy: Inscribed Angle Theorem Proof
Proving that an inscribed angle is half of a central angle that subtends the same arc.
CK-12 Foundation
Ck 12: Algebra Ii: 4.8 Pythagorean Identities
This section explores the Pythagorean Identity and how it applies to right triangles set inside unit circles, in terms of sine, cosine, and tangent functions.
Cut the Knot
Cut the Knot!: Polygons: Formality and Intuition
This is a very interesting site about polygons. The site begins by distinguishing between shapes whose sides intersect and polygons whose sides do not overlap. After this short introduction, you will find information regarding area and...
Wolfram Research
Wolfram Math World: Triangles
This site provides detailed overviews of many of the concepts and theorems associated with triangles. Content focuses on general triangles, cevians, triangle centers, triangle circles, and triangle lines.
CK-12 Foundation
Ck 12: Geometry: Arcs and Angles Study Guide
This study guide on arcs and angles covers key vocabulary, arc measurement in degrees and radians, congruent arcs, bisecting arcs, and the angles on, inside, and outside a circle. Also covers formulas and theorems. It is available for...
Wolfram Research
Wolfram Math World: Heron's Formula
This site provides a detailed overview of Heron's Formula. Content includes a definition, example, and formula.
Other
Platonic Realms: Conics
This resource provides in depth information on the conic sections. Click on the underlined words for definitions and diagrams.
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...
University of Georgia
University of Georgia: Inter Math: Triangle Inequality
This site has a description of the triangle inequality theorem along with a visual representation, and animation explaining the triangle inequality rule with the radii of circles at the segment endpoints. Links to related terms, more...
Geometry Help
Geometry Help: Chords
Explains the basic concept of chords with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
CK-12 Foundation
Ck 12: Geometry: Tangent Lines
[Free Registration/Login may be required to access all resource tools.] This concept teaches students about tangent lines and how to apply theorems related to tangents of circles.
TED Talks
Ted: Ted Ed: Why Are Manhole Covers Round?
Why are most manhole covers round? Sure it makes them easy to roll, and slide into place in any alignment. But there's another, more compelling reason, involving a peculiar geometric property of circles and other shapes. Marc Chamberland...
CK-12 Foundation
Ck 12: Geometry: Segments From Chords
[Free Registration/Login may be required to access all resource tools.] Looks at how to apply the Intersecting Chords Theorem.
Illustrative Mathematics
Illustrative Mathematics: G Co Classifying Triangles
The goal of this task is to help students synthesize their knowledge of triangles where only two of the vertices have been given. They will need to know that a triangle inscribed in a circle, with a diameter of the circle as one side, is...
CK-12 Foundation
Ck 12: Geometry: Segments From Chords
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to apply the Intersecting Chords Theorem to solve for missing segments from chords.
Walter Fendt
Walter Fendt: Thales' Circle
A short interactive activity to prove that a triangle inscribed in a semicircle is right-angled.
Illustrative Mathematics
Illustrative Mathematics: F Tf Special Triangles 1
Using known facts about the unit circle and isosceles triangles together with the Pythagorean Theorem, students can derive the sine and cosine of special angles. Aligns with HSF-TF.A.3.
Illustrative Mathematics
Illustrative Mathematics: F Tf Special Triangles 2
Using known facts about the unit circle and isosceles triangles together with the Pythagorean Theorem, students can derive the sine and cosine of special angles. Aligns with HSF-TF.A.3.
Texas Instruments
Texas Instruments: Real Numbers
Students learn to identify real numbers as rational numbers and irrational numbers. They review rational numbers as repeating decimals, and irrational numbers as non-repeating decimals. They also review commutative, associative,...
Mangahigh
Mangahigh: Pyramid Panic: Basic Shapes to Advanced Geometry
Guide a mummy safely through the burial chambers of a pyramid as you solve length and area problems in basic to advanced geometry. There are four game zones that deal with circles and triangles, quadrilaterals, the Pythagorean Theorem,...
Other
Dans Math: Lessons: Trigonometry
College professor Dan Bach reviews basic trig concepts, including trig functions, right triangles, circles, radians, and polar coordinates. Site includes animated graphs and detailed examples.
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.