Final answer:
Concepts of 3-core, reciprocity, and cosine similarity pertain to the network analysis field within computers and technology. The 3-core is related to the degree of nodes, reciprocity to mutual linkage in directed graphs, and cosine similarity to the angle between vectors representing nodes.
Step-by-step explanation:
The questions you've asked pertain to network analysis, which is a topic within the field of computers and technology, and often relevant in the study of social networks and data analytics. While I can't provide a direct answer without the specific details of the networks, I can explain the concepts:
3-Core of a Network
The 3-core of a network is a subgraph where each node has at least a degree of three. To find it, delete all nodes (and their associated edges) from the network that have a degree less than three. Continue this process iteratively until all nodes left have at least a degree of three.
Reciprocity of a Network
The reciprocity of a network is a measure of the likelihood of vertices in a directed graph to be mutually linked. It's calculated as the ratio of the number of links pointing in both directions to the total number of links in the graph.
Cosine Similarity
The cosine similarity between two nodes in a network is a metric used to measure how similar the nodes are. It is based on the cosine of the angle between two vectors of an inner product space that resemble the adjacency list of the nodes. Cosine similarity is often used in text analysis, where the vectors are usually the term frequency vectors of the documents.