Triangle+Congruency+I

Objective
Students will create a concept map of elementary triangle geometry, as assessed by rubric, to aid them in solving “The World’s Hardest Easy Geometry Problem”.

Standard
Georgia GPS MM1G3 Students will discover, prove, and apply properties of triangles, quadrilaterals, and other polygons. c: Understand and use congruence postulates and theorems for triangles (SSS, SAS, ASA, AAS, HL). MM1P1, Students will solve problems (using appropriate technology) b: Solve problems that arise in mathematics and in other contexts. c: Apply and adapt a variety of appropriate strategies to solve problems. MM1P3, Students will communicate mathematically. a. Organize and consolidate their mathematical thinking through communication. b. Communicate their mathematical thinking coherently and clearly to peers, teachers, and others.

Materials

 * Computer with Inspiration installed (per every 2 students)
 * Handout: “The World’s Hardest Easy Geometry Problem” reformatted from the web (link below) with my rubric on the reverse

Warm Up & Engagement
Give students the World’s Hardest Easy Geometry Problem ([|http://thinkzone.wlonk.com/MathFun/Triangle.htm]). Give them 10 minutes to play with it.

Lesson
(Having already learned about triangle congruence and similarity…)
 * 1) Divide up into previously defined collaborative teams of two students each.
 * 2) Direct the students to individually study the directions carefully for the hard geometry problem: “You may only use elementary geometry, such as the fact that the angles of a triangle add up to 180 degrees and the basic congruent triangle rules (side-angle-side, etc.). You may not use more advanced trigonometry, such as the law of sines, the law of cosines, etc.”
 * 3) Tell the class: Before we tackle the problem, we’ll need to outline exactly what the elementary geometry of triangles is. Your job today is to create a concept map, using your textbook, the bottom of this handout, and your own knowledge.

Assessment
Students will be graded on a group rubric for today’s work. I’ll be looking for the following:
 * That the geometry is correct
 * That the concept map connects related ideas
 * That the concept map shows evidence of organizing the information
 * That the elementary triangle geometry content is complete

Download a [|Word version of this lesson plan] Download a [|sample Inspiration concept map] Return to unit lesson plan page