My son is about to learn cosine in high school trig. He probably will roll his eyes and think: “what a waste of time.”

I made this walkthrough by hand to tell him that cosine is what powers vector databases.

Download t.co/MynVW7gV7T

Cosine → angle between vectors.

Cosine similarity → how embeddings are compared.

Vector database → finds the most relevant chunk by measuring which vectors point the same way.

That’s the math behind search, RAG, and agents everywhere.