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AD is median of triangle
( AD )^2 = ( 2 ( AB )^2 + 2 ( AC )^2 - ( BC )^2 )/4 ==> 64 = ( 2× 25 + 2 × 144 - ( BC )^2 )/4 ==> 256= 338 - ( BC )^2 ==> ( BC )^2 = 82 ==> BC = √82 cm
DC = √82 /2 = 4.53 cm
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