




 This is the first example in the file Geogebra quickstart provided by the author. The icon on the right links to this construction in an applet.





 The task is to construct the circumcircle of a given triangle.






 Choose the mode "Polygon" from the toolbar (click on the small arrow at the third icon from the left). Now click on the drawing pad 3 times to create the vertices A, B, and C. Close the triangle by clicking on A again.





 Step 2 Construct perpendicular bisectors






 Next, choose the mode "Line bisector" and construct 2 perpendicular bisectors by clicking 2 sides of the triangle.





 Step 3 Get the intersection






 In the mode "Intersect two objects" you can click at both perpendicular bisectors to get the intersection, which is the circumcenter of your triangle. To name it "M", click on it with the right mouse button and choose "Rename" from the contextual menu.





 Step 4 Construct the circumcircle






 To finish the construction, you have to choose the mode "Circle with center through point" and to click first at the center, then at any vertex of the triangle.





 Step 5 Alter the triangle






 Now choose the mode "Move" and use the mouse to change the position of any of the vertices  you will experience the meaning of "dynamic geometry".





 Get the original quickstart file to see more tips about this construction by the author.






