digital whiteboard android. ????Imagination is the core of intelligence. The use of multimedia teaching can not only extend and broaden the time and space dimension of teaching, but also provide students with rich emotional materials, and can further develop students' specific image thinking and cultivate students' imagination. For example, the derivation of the circular area formula, although the textbook provides experimental methods, but the experimental process is complex, difficult to operate, and a circle into a rectangular approximation is poor, causing many students to be skeptical about the derived formula. Due to the insufficiency of sensing materials, it is difficult for students to develop correct and reasonable imaginations and influence the formation of spatial concepts. We use the electronic whiteboard teaching software to divide the circle into several parts in turn, and to form the rectangles, parallelograms, triangles and trapezoids that we have learned. With the increase of the number of equal parts, the difficulty of the students' understanding - the process of approximating the length of the rectangle from the curve to the straight line is dynamically presented, thus accumulating rich sensing materials for students, providing a solid foundation for bold and reasonable imagination. . . The IQAio GR519 is an upgraded lightweight version based on the original IQAio GR511. The original dual-cavity structure was changed to a bottom-edge structure, so that the minimalist design accommodates modern classrooms and conference rooms. With one IQProjector V2 and one IQView E3821, you can achieve flexible and intelligent classroom.