Abstract
This paper focuses on the effective learning to understand the trigonometric ratio that is not able to be understood easily by students utilizing the RTMaC lesson study in the Japanese senior high school. We developed teaching materials and methods, and had the classroom practices about the definition of trigonometric ratio and a basic concept of trigonometric ratio. As a result, we confirmed that the teaching materials and methods elevate the students to understand the definition of trigonometric ratio and a basic concept of trigonometric ratio.
