In this tetrahedron model, you may vary: [br][list][*]its base (ABC) and the position of its altitude (D) (on the left); [/*][*]the apex (E) (on the right).[br][/*][/list][br]Drag X', Y' and Z' on the right to fold individual faces.

You may put the point D at specific centres of the base by using the command '[url=https://wiki.geogebra.org/en/TriangleCenter_Command]TriangleCenter[/url]' in the input bar. [br][br]For example, you enter 'D=TriangleCenter(A,B,C,1)', D will be the incenter of triangle ABC. [br][br]Similarly, 2 for centroid, 3 for circumcenter and 4 for orthocenter. [br]