抄録
The purpose of this study is to explore pupils' difficulties in understanding reflex angles. Two methods were used in this study. First, a questionnaire which included task items about measuring and drawing reflex angles with a protractor was given to 79 fifth-grade pupils. Clinical interviews were then conducted with eight selected pupils to verify their answers in more detail.
The results determined that about 60% of the pupils who answered incorrectly explained correctly how to do it. They seemed to understand reflex angles from addition or subtraction, according to angle size, as well as pupils who answered correctly. The study also revealed that they had difficulties in measuring or drawing reflex angles using a protractor upsidedown because they do not recognize that the size of angle can be determined by reversing the protractor's position.
