CHAPTER 2 Overcoming Mathophobia: Reading and Understanding Mathematical Expressions 23

for calculating that number’s factorial. To do that, you write down all the whole

numbers from 1 to the factorial number in a row, and then multiply them all

together. For example, the expression 5!, which is read as five factorial, means to

calculate 1

2

3

4

5 (which equals 120).

Even though standard keyboards have a ! key, most computer programs and

spreadsheets don’t let you use ! to indicate factorials. For example, to do the cal-

culation of 5! in Microsoft Excel, you use the formula =FACT(5).

Here are a few factorials fun facts:»

» ^{Factorials can be very large. For example, 10! is 3,628,800, and 170! is about}

7 3

10³⁰⁶

.

, which is close to the processing limits for many computers.»

» ^{0! isn’t 0, but is actually 1. Actually, it’s the same as 1!, which is also 1. That may}

not make obvious sense, but is true, so you can memorize it.»

» ^{The definition of factorial can be extended to fractions and even to negative}

numbers. But good news! You don’t have to deal with those kinds of factorials

in this book.

Absolute values

The term absolute value refers to the value of a number when it is positive (mean-

ing it has no minus sign before it). You indicate absolute value by placing vertical

bars immediately to the left and right of the number. So |5.7| equals 5.7, and

|–5.7| also equals 5.7. Even though most keyboards have the | (pipe) symbol, the

absolute value is usually indicated in plain text formulas as abs(5.7).

Functions

In this book, a function is a set of calculations that accepts one or more numeric

values (called arguments) and produces a numeric result. Regardless of typeset or

plain text, a function is indicated in a formula by the function name followed by a

set of parentheses that contain the argument or arguments. Here’s an example of

the function square root of x: sqrt(x).

The most commonly used functions have been given standard names. The preced-

ing sections in this chapter covered some of these, including sqrt for square root,

exp for exponentiate, log for logarithm, ln for natural log, fact for factorial, and abs

for absolute value.