Secondary mathematics teachers' knowledge of slope

This study, conducted m the United States, investigated secondary mathematics teachers' concept definitions, mathematical understanding, and pedagogical content knowledge of slope. Surveys were collected from 18 preservlce and 21 inservice teachers; 8 teachers from each group were also interviewed. Geometric ratios dominated teachers' concept definitions of slope. Problems involving the recognitlon of parameters, the interpretation of graphs, and rate of change challenged teachers' thinking. Teachers' descriptions of classroom instruction included physical situations more often than functional sltuataons. Results suggest that mathemahcs teacher educahon programs need to specifically address slope as a fundamental concept, emphasismg its connection to the concept of function.