Education Technology

Special Parallelograms

Activity Overview

In this activity, students will study special types of parallelograms like rhombus and rectangle, and investigate properties related to their diagonals.

Before the Activity

Install the Cabri™: Jr. App on the students' graphing calculators using one of these two methods:

  • TI-Connect™,  a TI Connectivity Cable, and the Unit-to-Unit Link Cable
  • TI-Navigator™  "send to class" feature
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 41 - 43 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the Activity procedures:

    Rhombus:

  • Draw a segment AC, construct its perpendicular bisector, and label the point of intersection as X
  • With X as center and XC as radius, draw a circle
  • Label the points of intersection of the circle and the perpendicular bisector as B and D
  • Hide the circle and connect the points A, B, C, and D to form rhombus ABCD
  • Measure the angles of the rhombus
  • Observe that the diagonals bisect the opposite angles
  • Alter the rhombus and verify this observation
  • If a parallelogram is a rhombus, then each diagonal bisects a pair of opposite angles


  • Rectangle:
  • Draw a segment AB and construct a perpendicular line through A
  • Place a point C on the perpendicular line through A
  • Construct a line perpendicular to AC through C
  • Construct a line parallel to line AC through point B, and label the point of intersection as D
  • Hide lines AC, CD, and BD
  • Draw the diagonals of the rectangle
  • Measure the diagonals and note that they are congruent
  • Alter the rectangle and verify this observation
  • If a parallelogram is a rectangle, then the diagonals are congruent
  • After the Activity

    Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary