
If BT is the midsegment of ΔMAH and DC is the midsegment of ΔBTH, then MA, BT and DC are parallel.
Therefore the segments form the proportion:

BT is the midsegment of ΔMAH, therefore

DC is the midsegment of ΔBTH, therefore

Substitute:

cross multiply

divide both sides by HM


cross multiply

divide both sides by HM
