Someone mentioned at the end of class today that they found calculus beautiful and time ran out before I could agree with them.
I try to not talk about economics because most people find the topic boring, and sometimes it is, but what makes it interesting and beautiful to me is that certain economic theories can, ceteris paribus, be proven to always be true because of calculus.
Above is a graphic representation of profit maximization in a perfectly competitive market. What makes it useful is that it expresses the optimum amount of goods to be produced--but what makes it beautiful is that this model can be used for any commodity in a similarly structured market. The model is beautiful because it is universal, and its universality is because of the underlying calculus governing each line on the graph.