Texas Instruments TI-73 41

Using the TI-73: A Guide for Teachers

Geometry

Activity

Have students perform the steps unless otherwise indicated.

1.On the transparency of the dolphin picture, label the x- and y-axes using whole numbers. Have students label their copies, too.

2.Lead the class in a discussion of selecting the first few key points to make a dot-to-dot outline of the dolphin. Depending on the level of your students, these points may be at whole number values, integral values, or fractional values.

3.Have students work with partners to complete the dot- to-dot outline of the dolphin. Ask: How could you get the curved lines smoother? (select points closer together, use fractional or decimal values for coordinates)

4.On the transparency, label the points in alphabetical order and as ordered pairs counter-clockwise around the outline of the dolphin. Have students label their copies.

5.Record the coordinates of each of those points on a sheet of paper.

6.Using the TI-73, enter the x-coordinates of the dolphin outline into L1 and the y-coordinates of the dolphin outline into L2.

a.Display the List editor.

b.If necessary, clear L1.

$ to highlight L1

: b

c.Starting from the first line in L1 , enter the x-coordinates. (You’ll get an error if L1 is still highlighted.) Press b after each list item.

d.Now follow the same procedure and enter the y-coordinates in L2.

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Depending on the level of your students, the dolphin may be in the first quadrant only or it may be in more than one quadrant.

Remember, for a closed figure, the first point’s coordinates need to be reentered as the last point, also.

It is critical that students enter the pairs of numbers in the proper order, because the order entered is the order in which they are plotted. You also need to make sure that both lists in each pair are the same length ( L1 and L2 are the same length).