This Demonstration illustrates the concept of rotating a 2D polygon. The rotation matrix is displayed for the current angle. The default polygon is a square that you can modify.

If two inscribed angles intercept the same arc, then the angles are equal. Drag the orange points to change the figure.

A dynamically simplified solar system is constructed from online data to explore the real solar system on many different scales.

The realistically scaled solar system is surprising because nothing is visible due to the presence of many different scales. That is why it is usually rescaled in animations or illustrations. This is nice but gives us a wrong sense of distances and sizes. This Demonstration is intended to show the solar system's different scales in their full glory.

Since it is hardly possible to see anything when the real scales are used, controls have been added to modify the sizes of the celestial bodies.

Algebra students need practice determining equations of lines given a pair of points, or the line parallel or perpendicular to a given line through a given point. This Demonstration, along with guiding worksheets or a teacher presentation, gives students a chance to see the relationships between these lines and points.