Using GeoGebra software we can construct hyperbolic figures, also we can perform measurements of lengths and of angles to investigate if the properties satisfied by some particular figures of Eucliden geometry are satisfied by the homologues figures in hyperbolic geometry. There are properties of Euclidean geometry that are preserved in hyperbolic geometry. For example: the vertical angles are equal and the sum of supplementary angles is 180°. This derives from the fact that the angle between two intersecting arches is defined by the angle formed by the two tangents passing through the intersecting point. Many other properties are not preserved such as those related to the distance. Also, in Euclidean geometry the sum of the angles of the triangle is constant. Not so in hyperbolic geometry. Play with the applet and observe the sum.
