Given: D, E, F are mid points of BC, CA and AB respectively. AB = AC
Let the point where AD and FE meet be G
Since, D and E are mid points of BC and CA respectively thus,
By mid point theorem, DE∥AB and DE=12AB
In △AFG and △DEG,
∠AGF=∠DGE (Vertically Opposite angles)
∠FAG=∠GDE (Alternate angles for parallel lines DE and AB)
DA=DE (D is mid point of AB)
Thus, △AFG≅△DEG (ASA rule)
Hence, AG=DG (Corresponding sides)
EG=FG (Corresponding sides)
Thus, AD bisects EF