proof for basic proportionality theorem

BPT(Thales Theorem) - 

Given - In triangle ABC,  DE is parallel to BC. DE bisects AB at D and AC at E.

To Prove - AD/BD= AE/CE

Construction - Join BE and CD and draw EF is perpendicular to AB and DG is perpendicular to AC.

Proof - 

As,  EF is perpendicular to AB, EF is the height of tr's ADE and DBE.

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