Computing numerical checks of certain relations between geometric objects in a planar construction is a well known feature of dynamic geometry systems. GeoGebra's newest improvements offer symbolic checks of equality, parallelism, perpendicularity, collinearity, concurrency or concyclicity. Also dragging of locus curves, defined explicitly or implicitly (or as an envelope curve) is a new feature in GeoGebra to visually check conjectures in planar geometry. By combining plotting and proving we can focus on some new possibilities to teach Euclidean geometry in the classrooms.
This GeoGebraBook was presented at the University of South Bohemia in České Budějovice at the 8th conference "The Use of Computers in Mathematics Education" on 10 November 2017. A plenary talk was also given before it in the same topic.