Using GeoGebra to confirm the solution
Sara acknowledged to have felt some difficulty in “explaining with words” how she
thought about this problem; therefore, she decided to send a screen capture containing
her construction in GeoGebra (Figure 4). According to her words, Sara “imagined” that
the rectangle had a length of 12 cm and then built a representation of the rectangular
garden and the triangular flowerbed, thoroughly following the statement. Therefore
she determined the area of the triangle (on the left) and recognized that it matched the
length of the rectangle that she initially chose. By making a second construction (on the
right) she was already aiming at justifying the earlier result by dividing the flowerbed
into two triangles, ONM and OMK. However, Sara explained that the 2m stick
corresponded to the base
of those smaller triangles,
and she represented their
heights using two
segments, a1 and b1.
Finally, she noted that
“adding” two segments,
i.e., the heights of the
smaller triangles, it gives
the length of the
rectangular garden.
Sara’s technological
fluency is quite evident in
terms of the effective use
of GeoGebra. It is also quite obvious in the diversity of tasks that she was engaged in
while solving this problem, as revealed by her desktop’s taskbar: she was also
“chatting” online, checking the SUB12’s webpage, and already drafting her answer.
Considering mathematical fluency, we highlight the language she used: aside the email
limitations regarding symbolic writing, Sara was clearly concerned with making
herself clear and she correctly presented formulas and calculations.