Redesigned, but original idea from http://tube.geogebra.org/material/show/id/157886 by Priyank.
( Total 1 hour's work for record)
Right angle emphasised correctly.
Added construction protocol, text comments and colours for explanation of steps. (This updated version has problems with displaying construction proctocols.
Download the file stored on my Google Drive at here or at https://drive.google.com/open?id=0B_CU802tZtF5TmRMWmNfd1M3Rnc
