let's focus on good definitions...”

## The Jacobian & Divergence

In which I try to change variables in multiple integrals using divergence theorem. I sort of succeed.

## The Jacobian & Determinants

I look into the source of using the Jacobian when we change variables.

## An Annotated History of the Reals

In the beginning, there was nothing, $$0 = \emptyset$$. Then we realized it was something, $$1 = \{ \emptyset \}$$. Then we wondered, why not have another thing? $$2$$. And another thing, $$3$$. And another, $$4$$, and another, $$5$$, and another, $$6$$, etc. Just like that, we had the natural numbers!1 And ...