The Geometer’s Sketchpad
®
for TI-89, TI-92 Plus, and
© 2000-2002 KCP Technologies, Inc.
13
Voyage™ 200 PLT User Guide and Reference Manual
Sketchpad’s
†
Transform menu lets you translate (slide), rotate (turn),
dilate (shrink or stretch), or reflect (flip). In this part of the tour, you’ll use
a reflection to construct an isosceles triangle.
Steps
Display
1. Start Sketchpad, or, if it’s started already, press
ƒ
Edit:
o
Sketch:
¨
New to open a new sketch.
2. Press
Š
(TI-89:
2 Š
)
@
until the Line tool (as opposed
to the Segment or Ray tool)
blinks, then press
¸
to
activate it.
3. Press
¸ @ ¸
to draw
a vertical line.
4. With the line still selected, Press
†
Transform:
©
Mark Mirror
to mark the line as the mirror across which you’ll reflect objects.
Sketchpad confirms this mark with a brief animation.
5. Choose the Point tool from the
toolbox:
Š
(TI-89:
2 Š
)
@ ¸
.
6. Move the cursor to one side of
the line and press
¸
to
construct a point nearby.
7. With the point still selected,
Press
†
Transform:
Ñ
Reflect (TI-89:
j
A
).
Sketchpad constructs and
displays the image of your point
reflected across the marked
mirror.
8. Press
N
to return to the Arrow, then drag either point to see how
its mirror image behaves. Try dragging the mirror and the points
defining it too.
Advanced Tour
In the previous introductory tour, you learned how to construct
an isosceles triangle using a Euclidean (compass and
straightedge) approach. In this section, you’ll use
transformations to construct another isosceles triangle. Then
you’ll investigate your triangle on a coordinate grid.
Transformational
Approaches
Reminder: A shortcut for
activating the segment tool
is
¥†
(TI-89:
¥y
).
Repeat the shortcut to scroll
through the palette of
straightedge tools.
Reminder: On the TI-89,
M
is a shortcut for
¸
when using tools and
selecting objects.
