GeoGebra is particularly useful for showing 3D objects in a dynamic way. Also, we can easily construct simple 3D geometric objects like cubes, cones, pyramids, prism and so on in GeoGebra.[br][br]The following is an example of a wedge, a type of 3D objects that we often use when teaching 3D trigonometry.[br]

[b][u]Classwork[/u][/b]: The following is a part of a question in HKDSE 2019 Math (Core part) Exam.[br][br]The following shows a tetrahedron ABCD. Let P be a point lying on AD such that BP is perpendicular to AD. A craftsman finds that AC = AD = CD = 13 cm, BC = 8 cm, BD = 12 cm and [math] \angle ABD=72\degree[/math]. [br][br]Find (i) [math]\angle BAD[/math], and (ii) CP

Draw this tetrahedron in the GeoGebra applet below. It is not easy![br][br][br]My solution is [url=https://www.geogebra.org/m/rbz3fpag]here[/url].