



 This page contains information about basic construction techniques. Click the file icons on the right to open individual viewlets.





 Geometric figures are constructed from basic elements such as points, lines (including segments and rays and circles. Free points can be dragged around without restriction while points on objects (lines or circles) have their movement restricted on the parent objects. Points are also created as intersections of objects. Lines and circles are defined by points. On the other hand, intersections of lines and circles define new points.






 Try some freehand drawing and get familiar with the tools and the behaviour of objects.






 Demonstrate drawing of lines, circles, and labeling. handling points with the selection/arrow tool.





 Use 'Construct' menu for specific constructions or shortcuts, such as parallel and perpendicular lines, midpoints, angle bisectors. These commands are available in most dynamic geometry software and are important tools for euclidean constructions. I call them 'shortcuts' because basically they can be obtained through lines and circles constructions (i.e., straightedge and compass constructions).






 Depending on the objects selected, certain commands on the 'Construct' menu are activated. For example, if you click to select a point and a line, you may construct a parallel line or a perpendicular line through the given point with respect to the given line.






 perpendicular lines; triangle interior






 angle bisector; perpendicular bisector





 Tips: When you finish drawing objects, always resume the selection/arrow tool for moving and selecting objects. Check carefully which objects are highlighted (selected) before any action. Very often, unnecessary objects are selected accidentally. If in doubt, click in the empty space to deselect everything and start all over again.





 Simple Measurement and Calculation






 measure length of segment and distance between points






 measure area of triangle and other polygon (interiors)






 measure circle (radius, circumference and area) and calculate ratio






 measure angle and calculate ratio






 Trace a point while it moves, this option can show temporarily a locus of a point.






 Split/Merge a point from/to a path (a line or a circle)






