Greatest Integer Function

The function used to find the greatest integer less than or equal to the given number is the greatest integer function. It is represented as ⌊x⌋ for the number x. Mathematically, the greatest integer function ⌊x⌋ is represented as: 
⌊x⌋ = n, where n ≤ x < n + 1, where n is an integer. 

For example, ⌊5.09⌋ is 5, since 5 ≤ 5.09 < 6.

In mathematics, real numbers can be rounded using the greatest and smallest integer functions. In this section, we will learn the differences between the greatest and smallest integer functions.

The properties of the greatest integer function are used to simplify and solve problems involving rounding. Some properties of the greatest integer function are:

• ⌊x⌋ = x, if x is an integer 

•  If I is an integer, ⌊x + I⌋ = ⌊x⌋ + I. That is, the greatest integer of (x + I) equals the sum of ⌊x⌋ and I.

• ⌊x + y⌋ ≥ ⌊x⌋ + ⌊y⌋, for any real numbers x and y, the greatest integer of their sum is greater than or equal to the sum of their individual greatest integers 
   

• If ⌊f(x)⌋ ≥ I, then f(x) ≥ I

• If ⌊f(x)⌋ ≤ I, then f(x) < I + 1

• ⌊-x⌋ = -⌊x⌋, if x is an integer 

• ⌊-x⌋ = -⌊x⌋-1, if x is not an integer

A number line can help visually represent the greatest integer function. In this section, we will learn how to represent the greatest integer function on a number line by following these steps: 

• First, we draw a number line and mark the numbers in equal intervals

• Then we mark the real number

• On the number line, the greatest integer of a number is the largest integer less than or equal to it, located to its left.

For example, ⌊4.9⌋

To represent ⌊4.9⌋ on a number line, start drawing the number line and mark the point 4.9. The greatest integer less than or equal to 4.9 is the number left to it, which is 4, the number immediately to the left. So, the ⌊4.9⌋ = 4

The greatest integer function is defined for all real numbers and outputs integers. The set of all real numbers (R) is the domain of the greatest integer function. The set of all possible output values is the range, and it is an integer.

The greatest integer function can be represented by a graph with a step structure. Hence, the graph is also called a step function. For understanding how to plot the function, consider f(x) = ⌊x⌋. Where, if x is an integer, then f(x) = x, and if x is not an integer, then f(x) ≤ x, the integer left to x. 

For instance, for any x in the interval [2, 3), f(x) = 2.
For any x the interval [-2, -1), F(x) = -2

In other words, for any integer n, all numbers in [n, n+1) have f(x) = n. When x reaches n + 1, the function value becomes n + 1. Thus, the graph has a step structure:

A solid dot at the point (n, n) indicates the value included, and the values excluded are indicated using a hollow dot at (n + 1, n)

The greatest integer function is used to convert continuous or fractional values into whole numbers. Here are some applications of the greatest integer function:

• In shipping and packing, the greatest integer function is used to calculate how many full boxes are needed to pack the items. For example, if we need to pack 47 items, and we pack 10 items per box, ⌊47 ÷ 10⌋ = 4, which means 4 boxes are required to pack. 

• In event planning, the greatest integer function helps with seating arrangements, planning food, scheduling and timing, and resource allocation. 

• In logistics, we use the greatest integer function for inventory management.