Functions are the core of algebra, and the teaching of function concepts is also the main task of high school mathematics Students' learning of functions and their concepts shifts from understanding specific quantitative relationships to understanding abstract quantitative relationships The monotonicity of functions, as the property of the first function that students learn in high school, lays a certain foundation for learning function related knowledge in the future.

The purpose of this paper is to discuss the innovative research on the instructional design and development of courses based on digital platforms. Firstly, the importance of digital platforms in the field of education and the current status of their application are introduced. Secondly, the concepts and key elements of course instructional design and development are analysed, and the role of digital platforms in course instructional design and development is discussed. Then, the innovative practices and methods of course instructional design and development based on digital platforms are described, including the integration and personalised customisation of learning resources, the construction and interactive communication of learning communities, and the improvement of evaluation and feedback.