**Here's the official definition:**

**Where n cannot be a decimal or a fractionor a radical or a negative number... n must be a whole number.**

*** 0! is specifically defined to be 1...**

**(If it isn't, our formulas in the next sections won't work!)**

**Yes, you have the button on your calculator, but, I'd like you to get comfortable working with these WITHOUT your calculator. Why?**

**Try popping 70! into your calculator.**

**That probably gave you an error... If it didn't, try 450! THAT should definitely be a problem!**

**On regular calculators, 69! is the biggest thing it can handle -- on graphing calculators, it's 449!**

**So, we need to learn to live without our calculators!**