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### Infinity

Mathematics uses the concept of **infinity**. It is written as ∞ for infinitely large and as Δ*x* for infinitely small. But beware, for it are not numbers. You can perform calculations with it. If only you know what you are doing, because there are sometimes really surprises.

##### Infinitely large

We must always take care that ∞ has no fixed value, so

This works the same way for every number, also for very large ones. And even for

You can perform subtractions

That works for every number, however

= ?

##### Infinitely small

We take care, that Δ*x*→0, so

as Δ*x* is neglectable. But here again you see