Education Technology

TI-92 + Cabri Geometry for the Not Necessarily Advanced User

Activity Overview

This activity is a tutorial on using the Cabri Geometry™ application. Students' perform geometric constructions which range from simple triangles to complex conics.

Before the Activity

  • Open the Cabri Geometry application on the TI-92 Plus / Voyage 200 calculator
  • Use the TI Connect™ and the TI Connectivity Cable to transfer data from the computer to the calculator
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 1 - 14 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the Activity Procedures:

  • Drag the ray of a right triangle around the vertex, and observe that it traces a circle
  • Understand that an angle inscribed in a semi-circle is a right triangle

  • Understand that the lines joining midpoints of adjacent sides of a quadrilateral form a parallelogram

  • Construct various quadrilaterals and angle bisectors for each quadrilateral

  • Construct an equilateral triangle and a point in its interior
  • Determine the distance of this point to each side
  • Make a conjecture about the relationship between the sum of these measures and the length of the altitude

  • Construct a triangle and locate midpoints of two of its sides
  • Draw an arbitrary point on the third side, and connect it to the midpoints of the other two sides
  • Make a conjecture about the areas of the resulting quadrilateral and two triangles

  • Construct a square and the midpoints of two consecutive sides
  • Plot a point on one of the remaining sides such that the distance from this point to the vertex opposite the chosen sides is one-fourth the length of the side of the square
  • Form a triangle by joining the three created vertices and hypothesize about the relation between the areas of the triangle and the square

  • Plot a point inside a circle and a point on the circle
  • Connect the two points with the help of a segment, and draw a perpendicular bisector to it
  • Join the point on the circle to the center, and label the point where it intersects the perpendicular bisector
  • Animate the plot on the circle and observe the traced out ellipse

  • Explore the ratios of the sides of a right triangle
  • After the Activity

    Students answer the questions on the activity sheet.

    Review student results:

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