\VDDdef M(0,0)L(-4,-4)R(4,4)
\VDDdcanvas1:1
   \VDDdcircle M:4               % some circle
   \VDDdeflinepoint l:RA(-5,1)
   \VDDdwholeline l              % some line
   \VDDcleadline m:l:M
   \VDDdwholeline m
   \VDDcintersect S:lm
   \VDDtriangleonesideotherangle P:SM:4,90 % find P
   \VDDctranslate Q:S:PS         % the other point is related
   \VDDcavg M':MQ
   \VDDllinelinepointletter lm:SM':1:1
   \VDDdeflinepoint n:QM
   \VDDllinelinepointletter mn:MP:1:1
   \VDDdperp QSM
   \VDDdline PMQ
   \VDDdlinepartequal QMPM
   \VDDlcirclelinepointletter l:MP:1:1
   \VDDlcirclelinepointletter l:MQ:1:1
\VDDdcanvasend
