## “Send me your rotation

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 some*thing*, \( 1 = \{ \emptyset \} \). 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 …