Lesson Plan
Texas Instruments

Texas Instruments: Investigate Triangles and Congruence

For Teachers 9th - 10th Standards
Students can use the TI-84 Plus family with Cabri Jr. to prove triangle congruence with SSA.
Activity
Other

Gobierno De Navarra: Puntos Y Rectas Notables De Un Triangle

For Students 9th - 10th Standards
Learn how to construct the bisectors, median and altitude of a triangle.
Activity
Texas Instruments

Texas Instruments: Triangle Inequality Theorem

For Teachers 9th - 10th
In this activity, students will explore the concepts underlying the Triangle Inequality Theorem by comparing side lengths and angle measures of a triangle. They will use an interactive construction to see why this theorem is true.
Activity
Texas Instruments

Texas Instruments: Got an Equilateral Triangle? With Cabri Jr.

For Teachers 9th - 10th Standards
Using the Compass tool in Cabri Jr., students will construct an equilateral triangle, and check the length of each side. When a vertices is moved using the Alpha hand, the triangle remains equilateral.
Handout
Math Open Reference

Math Open Reference: Congruent Triangles

For Students 9th - 10th Standards
A complete reference guide to congruent triangles. It provides definitions, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Activity
Texas Instruments

Texas Instruments: Asa Triangle Congruence

For Teachers 9th - 10th Standards
Students construct and analyze triangles that are congruent by ASA.
Activity
Texas Instruments

Texas Instruments: Centers of a Triangle

For Teachers 9th - 10th
The centroid, circumcenter, orthocenter, and incenter are the four classic centers of a triangle that are studied in geometry. In this activity, you will construct these center points and discover their properties. [Requires Adobe Reader.]
Activity
Maths Challenge

Maths challenge.net: Perpendicular Construction

For Students 9th - 10th Standards
This is a "three star" geometry problem where prior math problem skills and proof experience is recommended to solve this "Perpendicular Construction" problem.
eBook
CK-12 Foundation

Ck 12: Interactive Geometry: 5.5 Geometry Software for Constructions

For Students 9th - 10th Standards
Use interactive geometry software to construct an equilateral triangle that maintains its shape even if you move its vertices.
Unknown Type
Khan Academy

Khan Academy: Triangle Side Length Rules

For Students 7th Standards
Practice solving problems with triangle side length rules.
Interactive
National Council of Teachers of Mathematics

Nctm: Illuminations: Circumcircle

For Students 9th - 10th
This applet allows for the construction and exploration of a circumcircle.
Activity
Texas Instruments

Texas Instruments: Dynamic Geometry: Basic Constructions

For Teachers 6th - 8th Standards
Students use the Cabri Jr. application to draw triangles and construct perpendicular bisectors on the sides of a triangles. They study the properties of a triangle and understand how the measures of angles of a triangle is always 180...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Origami Equilateral Triangle

For Teachers 9th - 10th Standards
The purpose of this task is to explore reflections in the context of paper folding. Each fold is associated with a line of reflection and understanding each step in the construction requires careful analysis of angles and of the...
Activity
Texas Instruments

Texas Instruments: Simple Constructions With Cabri Jr.

For Teachers 9th - 10th
The Cabri Jr. Constructions Tools Menu (F3) contains tools for contructing geometric objects. This activity provides practice using several of the tools. The activity also investigates the terms: median of a triangle and the altitude of...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: g.c Inscribing a Circle in a Triangle Ii

For Teachers 9th - 10th Standards
This task focuses on a fact which comes out of the construction of the inscribed circle in a triangle: the angle bisectors of the three angles of triangle ABC all meet in a point. Aligns with G-C.A.3.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Inscribing an Equilateral Triangle in a Circle

For Teachers 9th - 10th Standards
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.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Reflected Triangles

For Teachers 9th - 10th Standards
In this task, students must use a straightedge and compass to construct the line across which one triangle was reflected onto another. Aligns with G-CO.A.5 and G-CO.D.12.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G C Circumcenter of a Triangle

For Teachers 9th - 10th Standards
The goal of this task is to construct the circumcenter of a triangle, that is, the point which is the same distance from each of the triangle's three vertices. This task shows that the three perpendicular bisectors of the sides of a...
Activity
Texas Instruments

Texas Instruments: Altitude, Median, and Angle Bisector of a Triangle

For Teachers 9th - 10th
In this activity, you will construct special segments of a triangle named altitudes, medians, and angle bisectors, Using their definitions. You will look at how an altitude, a median, and an angle bisector divide the area of a triangle....
Activity
Texas Instruments

Texas Instruments: The Orthocenter of a Triangle

For Teachers 9th - 10th Standards
Students understand that the orthocenter is the point of concurrence of the three altitudes of a triangle. They construct circumcircles and Feuerbach circles and determine the relationship between them.
Unit Plan
Oswego City School District

Regents Exam Prep Center: Reference Angles and Triangles

For Students 9th - 10th
The mathematics session investigates reference angles and triangles. The tutorial consists of class notes, examples, and practice problems with solutions. The teacher resource includes a worksheet on the construction of skateboarding ramps.
Activity
Texas Instruments

Texas Instruments: Exploring the Circumcenter of a Triangle

For Teachers 9th - 10th Standards
In this activity, students develop an understanding of the circumcenter of a triangle. Students construct perpendicular bisectors of three sides of a triangle and find the circumcenter.
Activity
Texas Instruments

Texas Instruments: Exploring the Orthocenter of a Triangle

For Teachers 9th - 10th
In this activity, students use the Cabri Jr. tools to draw altitudes in a triangle. They construct a line perpendicular to a given line and through a given point. [Requires Adobe Reader.]
Website
PBS

Pbs Learning Media: Triangles: Designing a Straw Bridge

For Students 3rd - 8th
In this video segment adapted from ZOOM, the cast tries to design and build a bridge made out of drinking straws that will support the weight of 200 pennies. [4:02]

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