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Forum URL: http://www.cut-the-knot.org/cgi-bin/dcforum/forumctk.cgi
Forum Name: College math
Topic ID: 739
Message ID: 2
#2, RE: Areas Of Two Special Triangles And Pythagorean Theorem
Posted by alexb on Aug-03-10 at 11:22 PM
In response to message #0
Lemma is pretty simple:

(FDE) = ((ADE) + (CDE))/2.

(ADE) = (ABD) and (CDE) = (BDE).