ATP verification, getting a sufficient condition

In general diagonals of a parallelogram bisect each other.
Use GeoGebra's proving subsystem to get sure answers:
  1. Enter Text[Prove[g==h]] to learn if g and h are of equal length in general (i.e., in most cases). (The Text command helps to show the output in the Graphics View since the output of the Prove command is shown in the Algebra View by default.
  2. Click on the output and move it away to see the output for the next statement you type. Now enter Text[ProveDetails[g==h]] to get some information of sufficient conditions whether g and h are of equal length. How can you interprete the result?