prev

next

out of 14

View

221Download

5

Embed Size (px)

South African Journal of EducationCopyright 2012 EASA

Vol 32:26-39

Learners engaging with transformation geometry

Sarah Bansilal and Jayaluxmi NaidooDepartment of Mathematics, University of KwaZulu-Natal

Bansilals@ukzn.ac.za

This article reports on a qualitative, interpretivist study that focused on the use ofvisualisation and analytic strategies by Grade 12 learners when working withproblems based on transformation geometry. The research was conducted with 40learners from a Grade 12 class at one high school in the north Durban area ofKwazulu-Natal. Participants completed a written task and a smaller sample of theparticipants engaged in investigative semi-structured interviews with the resear-chers. The framework for the study was based on transformations of semioticrepresentations as well as the visualiser/analyser model. The findings revealed thatmost learners performed treatments in the analytic mode when responding to thetasks, and showed limited movement across the two modes which are essential fora deepening of understanding. The study identified one learner, however, who wasable to move flexibly between the modes and who displayed a deep understandingof the concepts. The article concludes by recommending that opportunities need tobe created for learners to engage in transformation geometry activities which em-phasise conversion.

Keywords: analysis; conversions; transformation geometry; transformations;treatments; visualisation

IntroductionWithin the current (2011) South African curriculum, school mathematics incorporates trans-formation geometry, which was introduced in the Further Education and Training (FET) bandin 2006. This strand allows learners to make connections across other geometries within thespace, shape and measurement learning outcome, as well as with algebra and trigonometry.These connections are intended to create a more integrated, holistic knowledge of mathematics(DoE, 2003) and to allow for novel interpretations of the mathematics learnt in the otherstrands. It was this characteristic of the multiple connections between the strands that this studywas focused on, to find out more about the strategies that Grade 12 learners used to solveproblems in transformation geometry. By studying the learners visual strategies, we also hopeto develop an understanding of how learners use of visualisation techniques could contributeto more effective problem solving. We also hope that the study will inform teachers and cur-riculum developers about possible pedagogic approaches that could be used successfully whenteaching this strand of mathematics. Unfortunately the strand of transformation geometry hasbeen removed from the FET band from 2012 onwards (DBE, 2011). However the strandremains in the curriculum for Grades R to 9, and will still provide rich learning opportunitiesfor the learners in these grades.

This article reports on a qualitative, interpretivist study focusing on the use of visua-lisation and analytic strategies by Grade 12 learners when working with problems based ontransformation geometry. It addresses the effectiveness to which learners use either strategy,or both.

South African Journal of Education, Volume 32(1), February 2012 27

Literature reviewThere is limited available research on learners understanding and learning of transformationgeometry. In one such study Edwards (1997) maintains that transformation geometry providesan ample opportunity for learners to develop their spatial visualisation skills and geometricalreasoning ability. She used transformation geometry tasks to document the learning path of thestudents in a computer based micro-world. Edwards (2003) identified a particular miscon-ception about rotations. She found that instead of seeing rotation as mapping all the points ofthe plane around a centre point, the students in her study expected the shape to slide to thegiven centre point and then turn around it- showing that they had a hard time seeing rotationas occurring at a distance from the object (Edwards, 2003:7). Another study (Sproule, 2005)was carried out with Grade 7 learners, and sought to identify the strategies that were best ableto support learners in correctly completing reflection tasks. Sproule found that although mea-suring distances in the diagrams was the most common strategy used by the learners, thoseparticipants who folded along the axis of symmetry were the most successful. He speculatedthat the act of seeing the fold lines may have added to their success. In this study we envisionedinvestigating something similar, whether learners use of visualisation strategies could improvetheir success in solving transformation geometry problems. Other strategies that were utilised(Sproule, 2005) in solving the problems on reflections were the use of grid lines, measuring,drawing in marks, turning the figure, mental folds and using the mirror. Whilst Sproule focusedprimarily on completing reflection tasks, we developed a transformation geometry task thatencompassed reflection, rotation, translation, enlargement and investigations on the Cartesianplane. With the increased scope of our tasks we anticipated that the strategies employed by thelearners to complete our tasks would be different, because we were of the opinion that the toolsavailable would influence the learners way of thinking. The transformation geometry strandprovides an opportunity for assessing the use of skills and abilities in merging algebraic andgeometric ideas. This strand of the mathematics curriculum also encourages a visual as wellas an analytic approach, and provides a context for combining algebra and geometry. Thecombination of approaches, if any, would be more prevalent with Grade 12 learners, since byGrade 12, learners would have been exposed to both visual and analytical strategies.

The visual approach is one which advocates investigations and discovery of properties viaconcrete manipulations, models and diagrams. Within learning environments, opportunities thatexploit the visual mode of thinking ought to be sought (McLoughlin, 1997). A diagramprovided on the Cartesian plane may elicit visualisation strategies provided the student is ableto recognise what is given. However these strategies can be supported by the analytic approachwhich is characterised by general formulae to describe the results of transformations on figuresthat are situated within the Cartesian plane. In a situation where written instructions about ageneral point are given, we were curious about whether the mode of presentation would elicitanalytic or visual strategies.

The analytic approach seemed to be compelling to learners because of the ready avail-ability of formulae. Nevertheless, using generalised formulae to work out problems based ontransformation geometry is not as simple as learners perceive it to be. One of the importantcontributors to learners success in working with transformations is their procedural fluencyin algebraic procedures. Procedural fluency is a facet of mathematical proficiency and isdescribed as skill in carrying out procedures flexibly, accurately, efficiently and appro-priately (Kilpatrick, Swafford & Findell, 2001:107). Because analytic strategies in trans-formation geometry are dependent on the use of algebraic rules, learners misapplication of

28 South African Journal of Education, Volume 32(1), February 2012

rules can be largely attributed to poor algebraic skills. Many errors uncovered in the study [notreported in this paper] were related to learners inefficient use of algebraic manipulations(Naidoo & Bansilal, 2010). Although learners may know the rules for working out the resultsof translations, rotations and reflections, their poor algebraic skills may let them down.

In order to successfully use analytic techniques, learners would need to firstly know therules, understand the meaning of the algebra used in the rules, and be able to apply the rulesusing the given points. For these learners who struggle with the basics of algebra, they wouldnever be able to move past the first step, and would perform disastrously in questions intransformation geometry, because of their poor background knowledge.

An alternative approach is the use of visual strategies. These are ways of improvingcommunication by using scaffolds that can be seen. There are different types of scaffoldswhich include natural environment cues, body language, traditional tools and specificallydesigned tools. In empirical research with high school students in the US, Presmeg (2006)identified five types of imagery, which are concrete imagery, kinaesthetic imagery (of physicalmovement), dynamic imagery, memory images and pattern imagery. She found that concreteimagery was the most prevalent, with dynamic imagery (where the image itself is moved ortransformed) being used effectively but very rarely. This study will show evidence of onelearner exhibiting the use of dynamic imagery.

Dreyfus (1991:33) argued that the status of visualisation in mathematics should be andcan be upgraded from that of a helpful learning aid to that of a fully recognised tool forlearning and proof. His words convey a sense that many mathematics educators accordvisualisation a low status in their classrooms, which may explain why many learners arereluctant to use visualisation in mathematics. These words also suggest that teachers do notclearly distinguish between visualisation skills as such, and the strategy of visualisation as areasoning process or tool.

Breen described two types of thinking as (1997:97) The one was a tendency towardsabstraction The other was a tendency towards intuitive understanding which stressesprocesses of visualisation and imagery. Here, there is an inference that visualisation isrelegated to the senses, as if not involved in reasoning.

In fact, even the well-know