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The exterior bisector of the angle A of triangle ABC meets BC on D than prove that AB/AC=BD/BC |
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Answer» GIVEN: ABC is a triangle; AD is the exterior bisector of 4A and meets BC produced at D; BA is produced to F. Construction: Draw CE||DA to meet AB at E. Proof: In A ABC. CE||AD cut by AC. ∠CAD = ∠ACE (Alternate angles) Similarly CE || AD cut by AB ∠FAD = ∠AEC (corresponding angles) AC = AE (by isosceles △ theorem) Now in △BAD, CE || DA AE = DC (BPT) AB BD But AC = AE (proved above) AC = DC AB = BD or AB/AC = BD/DC (proved). |
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