AM is the median drawn from the vertex A to BC,
Applying the triangle inequality in the triangle ABM
AB + BM > AM —---(i)
Applying the triangle inequality in the triangle AMC
AC + MC > AM -----(ii)
Adding equations (i) and (ii) we get,
AB + BM + AC + MC > AM + AM
AB + AC + (BM + MC) > 2AM
AB + AC + BC > 2AM