Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Properties of Congruent Triangles

For Teachers 9th - 10th Standards
The goal of this task is to understand how congruence of triangles, defined in terms of rigid motions, relates to the corresponding sides and angles of triangles. Aligns with G-CO.B.7.
Handout
CK-12 Foundation

Ck 12: Geometry: Triangle Congruence Study Guide

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] Provides an overview of triangle congruence, including key terms, properties of congruent triangles, triangle postulates and theorems, and special triangles.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Showing a Triangle Congruence: A Particular Case

For Teachers 9th - 10th Standards
Given two congruent triangles, students are asked to analyze the effects of different transformations. Aligns with G-CO.A.5.
eBook
CK-12 Foundation

Ck 12: Interactive Geometry: 13.3 Sas Triangle Congruence

For Students 9th - 10th Standards
See how two triangles are congruent it means that all corresponding angle pairs and all corresponding sides are congruent.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Gpe, G Srt Finding Triangle Coordinates

For Teachers 9th - 10th Standards
Given a picture of a triangle on a coordinate grid, young scholars are asked to find the coordinates of points which divide line segments in a given ratio. Aligns with G-GPE.B.6 and G-SRT.B.5.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Why Does Sas Work?

For Teachers 9th - 10th Standards
For this task, students must explain the given reasoning for why triangle ABC is congruent to triangle DEF using the language of reflections. Aligns with G-CO.B.8.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Why Does Sss Work?

For Teachers 9th - 10th Standards
In this task, students must show that two triangles are congruent given a set of steps which produce a rigid transformation of the plane. Includes an experimental GeoGebra worksheet that instructors can use to demonstrate the task....
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: g.co Reflections and Isosceles Triangles

For Teachers 9th - 10th Standards
This task has learners link their intuitive notions of symmetries of a triangle with statements proving that said triangle is unmoved by applying certain rigid transformations. The mechanism through which students do this is via...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Gpe, G Srt Slope Criterion for Perpendicular Lines

For Teachers 9th - 10th Standards
The goal of this task is to use similar triangles to establish the slope criterion for perpendicular lines. Aligns with HSG-GPE.B.5 and HSG-SRT.B.5.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Srt Tangent Line to Two Circles

For Teachers 9th - 10th Standards
The purpose of this task is to use similar triangles and setting up a proportion in order to calculate a side length. Aligns with G-SRT.B.5.

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