On elements in small cocircuits in minimally k-connected graphs and matroids

We give a lower bound on the number of edges meeting some vertex of degree k in terms of the total number of edges in a minimally k-connected graph. This lower bound is tight if k is two or three. The extremal graphs in the case that k=2 are characterized. We also give a lower bound on the number of elements meeting some 2-element cocircuit in terms of the total number of elements in a minimally 2-connected matroid. This lower bound is tight and the extremal matroids are characterized.