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Geometria
Interactive Geometry Software
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Click the
Open Problem
button and select the file
beetle.xml
in the
vanilla
folder.
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Here's the
problem:
A beetle crawls on the surface of this pyramid from some point on edge AC
up to the top so covering a distance double to the height of the pyramid.
Reconstruct the beetle's path.
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Click the
Create Solution
button to start solving the problem.
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In
Geometria,
measurements and drawings can only be done on the surface of the figures.
However, the height of the pyramid is contained in its interior.
To be able to measure the height, we will have
to cut the pyramid with a plane through D perpendicular to the pyramid's base.
We will do that in 3 steps.
First, draw a pependicular through D to BC. Click the
Draw Perpendicular
button and fill in the labels.
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Second, draw a perpendicular through E to BC. The easiest way to do that,
by the way, is to select point E and segment BC (hold down the Ctrl
key as you do that), popup a menu and select
Draw Perpendicular
from that menu.
Choose the face in which to draw the perpendicular.
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Third, cut the pyramid through points D, E, F. Again, to save time,
select segments DE and EF, popup a menu and select
Cut Figure
from that menu.
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Select one of the two fragments of the pyramid, say Figure 1, and draw
a perpendicular through its apex to its base. This would be the height
of the pyramid.
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Measure the height and assign a variable to the result. The variable
will be copied to the notepad.
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Now, select again the pyramid, double the the variable Height
and lay that distance off D to AC. Again, to save time, have the variable
selected on the notepad, as well as point D and segment AC in figure Pyramid.
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Select
Answer
from the
Edit
menu and enter G, D, separated by a comma. Again, no input will be necessary
if you have points G, D selected ahead of time.
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