# MDM4U First Day! 2016-02-08

Another semester of Data Management is off to a great start! Today we learned a few “gentle” concepts and terms:

Tree diagrams – representing stages in a series of choices by branching for each option available. We used these to model all of the options for arranging letters, selecting unfashionable outfits, etc.

Factorials – the product of consecutive whole numbers, starting at 1. The formal definition I gave you was something like this:

$n! = n \times (n-1) \times (n-2) \times \dots \times 2 \times 1$ where $n \in \{ \mathbb{Z} | n \geq 0 \}$.

That is, for a whole number $n$, we calculate the factorial of $n$ by taking the product of all the natural numbers up to and including $n$.

For example, $5! = 5 \times 4 \times 3 \times 2 \times 1 = 120$.

We didn’t talk about it today, but we also need to define $0! = 1$. If you read this blog post, you’ll be able to casually mention that tomorrow as though it’s completely obvious. :)

I also handed out a course outline and a contact information/learning profile sheet for you to complete and return for me. Here are copies, just in case you need them:

Course Outline – MDM4U

Contact Information – MDM4U