Magnifying Glass on Cosine Function and Riemann Sums

① This example demonstrates a draggable 'magnifying glass' window that zooms into a local region of the cosine function graph, while simultaneously displaying the corresponding Riemann sums (upper and lower sums) as bar charts. ② Core mathematical concepts include trigonometric functions (cosine), Riemann sums (upper and lower), bar charts, and plane figures, helping students understand the geometric meaning of integral approximation. ③ Construction highlights: using GeoGebra commands such as Textfield, Point, Polygon, Segment, Line, and If to build the interactive interface; objects include function f, text field, point A, parameter h, magnifier (Lupe), multiple polygons (Ar, Al, StDreieck, etc.), auxiliary segments (sek_l, sek_r), and sliders (sl, sr) for dynamically adjusting interval and partition count. ④ Suitable for high school or pre-university students learning introductory calculus, function graphs, and numerical integration, as well as for teachers demonstrating the convergence of Riemann sums in class.