Question

in triangle ABC, D,E and F are the mid poinys of AB , BC and CA. if perimeter of triangle DEF is 7.2 cm, find the perimeter of triangle ABC​

Answer 1

Let G be the centroid of triangle ABC. Given E and F are the mid points of BC and AC respectively. Thus, by mid point theorem, AD∥EF

AB=2EF

AD=EF (I) (D is mid point of AB)

Now, In △ADG and △GEF,

∠AGD=∠EGF (Vertically opposite angles)

AD=EF (From I)

∠ADG=∠GFE (Alternate angles for parallle lines EF and AD)

△ADG≅△EGF (ASA rule)

Thus, AG=GE (Corresponding sides)

Also, DG=GF (Corresponding sides)

Thus, AE and DF bisect each other at G.

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