Notation

Types of notation

Notation is mainly made of letters, symbols, figures, and signs. Notation can use symbols, letters only, numbers only, or a mixture like the factorial symbol n!. Let’s look at some basic notation.

Counting notation

While studying maths, you are likely to come across the notation n!. This represents the factorial.

n! = 1 if n = 0

Otherwise \(n! = n \cdot (n-1) \cdot (n-2) \cdot (n-3) \cdot ... \cdot 3 \cdot 2 \cdot 1\)

n! counts the number of ways to arrange n distinct objects. So it is intuitive to know that when you have zero (0) objects, there is only one way to arrange them – do nothing.

Related to factorials is the binomial coefficient notation \(\Bigg(\begin{array} n n \\ k \end{array}\Bigg)\).

\(\Bigg(\begin{array} n n \\ k \end{array}\Bigg) = {^n}C_k = \frac{n!}{(n-k)!k!}\)

The formula above is a way to express the number of k subsets in an n set. So here we think of n as a non-negative integer and k as a non-negative integer which is less than or equal to n.

Set notation

This system is used to define the elements and properties of sets using symbols. We write down our sets as elements inside curly brackets.

For example, S = {1, 2, 3} is used to declare that 1, 2, and 3 are elements inside a set (S), whose elements are listed in the curly brackets.

We can have another scenario where S = {1, 2, 3, ......, n}.

Or write the same thing as \(S = {x | 1 \leq x \leq n}\)

The first expression states that a group named S contains the number from 1 to n.

The second expression states that a group named S is equal to the elements x such that x exists between 1 to n. The second expression says nothing about the number progression. The variable x can be any number between 1 to n such as 1.5, while in the first, 1.5 is not a member as the list jumps from 1 to 2.

There are a few symbols below we use when describing sets. The symbols apply left to right as the equal symbol, so a ∈ A will read “member a exists or is an element or the group / set A”

Numbers are not the only things that qualify as elements in sets. Pretty anything you want to talk about can. For example, if A = {a, b, c}, it can be written to denote that a is an element of the set A as a ∈ A. Sets themselves can be elements in other sets. We can use the notation {a, b} ⊆ A to note that {a. B} is a subset of A.

Summation notation

Summation notation is a convenient form to express long sums. For example, 1 + 2 + 3 + 4 + 5 could also be written as \(\sum^5_{i=1}{i}\). This means that we are summing up all the values of i starting from i = 1 until we get to i = 5, which is where we stop.

Pi notation

Pi notation is used to indicate repeated multiplication. It is also called product notation. This notation is quite similar to summation notation. An example is given below.

Index notation

This form of notation in mathematics is used to denote figures that multiply themselves a number of times.

Using index notation 3 · 3 can be written as 3² which is the same as 9. 3² can be read as three to the power of two. In the expression “the number that is raised to the power of X”, X is the number of times that the base number multiplies itself.

Index notation is also useful to express large numbers.

Qualities of notations

For notations to function, they need to possess certain qualities. These are discussed below.

• Uniqueness: this property establishes that one notation represents one specific thing only. This eradicates the potential harm of synonyms and ambiguity in the discrete area of mathematics.

• Expressiveness: this means the clarity of notation. Correct notation should contain all relevant information in the exact manner that it should be used. For example, an index notation can be expressed as 4² which is the same as 4 · 4. Writing the notation but leaving out the power doesn’t make it the same as 4 · 4.

• Brevity and simplicity: Notations are as brief and straightforward as possible. There is a chance mistakes may be incurred while writing long ones and considering the nature of precision they require to be valid, they need to be easy to read, pronounce and write.