수학과 교육과정과 교과서에 제시된 ‘삼각형의 세 각의 크기의 합’

Abstract

The sum of angles of a triangle is accessible in both the shapes area and the measuring area, where both approaches from different positions. This study explored how ‘the sum of angles of a triangle’ has been suggested in the mathematics curriculum and math textbooks from the past math curriculum to the present. First, the mathematics curriculum analyzed how the content was described and what area was placed from the 5th curriculum when this content began to be explicitly presented. In the 5th, 6th, and 7th mathematics curriculum, it was placed in the 'shapes' area, and in the 2007 revised, 2009 revised, and 2015 revised curriculum, it has been placed in the 'measuring' area. In terms of the content description of the curriculum, the sum of the three angles of the triangle was approached by deductive reasoning as a principle of Euclidean geometry or by inductive reasoning through angles measuring. Second, in the mathematics textbook, the learning series and introduction methods presented from the 1st to the 7th and the current 2015 revision were analyzed. It was possible to find the method by collecting three angles on a flat angle 180 degrees and the method by measuring the sum 180 degrees of three angles. In one area of ‘shapes and measuring’ in the 2022 revised curriculum, follow-up discussions are needed on how to approach the ‘sum of the three angles of the triangle.’