Median length theorem
Submitted by Structure on Sat, 12/29/2007 - 18:25.
Let ABC a triangle and a=length(BC),b=length(CA),c=length(AB).
Let M be the middle of BC and D symmetric of A with respect of M.
Then ABDC is a parallelogram.
From cosine theorem we have
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In triangle ABD we have
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Summing up we have
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Finally
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