The connotation of the concept refers to the essential characteristics of the object reflected by the concept; The extension of the concept refers to the object of the essential attribute reflected by the concept. The connotation of the concept is qualitative and the extension of the concept is quantitative, which shows what the concept reflects. The connotation and extension of the concept are unity of opposites, and the connotation is clear, then the extension is clear; Clear extension means clear connotation. For example, in the popularization of the concept of four angles in the new curriculum, the connotation of the concept of angle is a graph formed by a ray rotating from one position to another around the endpoint in a plane, and the extension refers to the classification of angles: positive angle, negative angle and zero angle. In teaching, the extension of concepts can be clarified through variations.
Example: the teaching of functional parity (People's Education Edition A)
The parity of function is the content of compulsory 1, and it is an important property after monotonicity of function. In the textbook, the concept of even function is obtained through specific functions.
Through, the concept of odd function was obtained. In the textbook, students are required to judge the parity of functions through Example 5. The author thinks that the extension of the concept of functional parity has not been really clarified through such exercises.
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