8-5 Lesson Plan Class 9th grade Geometry Honors Topic ...

Class 9 th grade Geometry Honors
8-5 Lesson Plan
Topic: Properties of Trapezoids (Using Geometer’s Sketchpad)
Alexis Graham
March 20, 2013
Standards: G.SRT.5 Use congruence and similarity criteria for triangles to solve problems
and to prove relationships in geometric figures.
Objectives: The student will be able to verify and apply properties of trapezoids.
Context: After teaching this unit, students will thoroughly understand the properties of
isosceles trapezoids. This is an inquiry lesson because students will be
discovering properties of isosceles trapezoids on their own. This activity covers
the following standards for mathematical practice: modeling with mathematics,
using appropriate tools strategically, and attending to precision.
Materials: Textbook, Calculator, Smart Board, Paper, Pencil, Geometer’s Sketchpad
Instructional What is a trapezoid? – A quadrilateral with exactly one pair of parallel sides
Sequence: The parallel sides are called bases, and non-parallel sides are called legs. The two
angles that share a base are called base angles. Notice that there are two pairs of
base angles in a trapezoid.
Students will be asked to construct an isosceles trapezoid in Geometer’s
Sketchpad. After constructing a basic isosceles trapezoid, students will make
manipulations to the trapezoid in an effort to change the leg lengths, but will
discover this is impossible with the properties of an isosceles trapezoid. Students
will then be asked to construct the diagonals of an isosceles trapezoid and
measure them, finding that they are equal in length. Students will drag the
trapezoid, changing the size and dimensions, but noting that the legs and the
diagonals remain the same length. Students will then be asked repeat the above
procedure measuring base angles, and find that the measure of the base angles
in an isosceles trapezoid have the same measure.
After students have finished with the technology portion of the lesson, they will
be given guided notes to complete regarding what they have just witnessed
using Geometer’s Sketchpad.
Assessment: Throughout the lesson, there will be checkpoints. Students will be asked
questions to answer questions regarding what is on their screen because this is

Alexis Graham
March 20, 2013
an individual assignment. After each construction students are also supposed to
check with the teacher, and write a conjecture about their measurements since
notes are only given afterward the technology portion of the lesson. At the
beginning of the next class, students will have an admit slip with applied
questions regarding properties of trapezoids.
References: Bennett, Dan. Exploring Geometry with The Geometer's Sketchpad. Emeryville,
CA: Key Curriculum, 2002. Print.