In Ruby 2.5.0, the **`Integer.sqrt()` function** returns the *integer square root* of a non-negative integer. 
This function returns the *largest positive integer* which is less than or equal to the square root of that number. 

Figure 1 shows the mathematical representation of the `Integer.sqrt()` function.

# Syntax
```ruby
Integer.sqrt(number)
```
# Parameter
`Integer.sqrt()` requires a non-negative number as a parameter. Otherwise, a `DomainError` occurs.

# Return value
`Integer.sqrt()` returns the integer square root of the number sent as a parameter. 

This is almost equivalent to:

```ruby
Math.sqrt(n).floor()
```

# Example

#example

#integer square root
print "sqrt(4):", Integer.sqrt(4), "\n"
# output = 2
print "sqrt(5):", Integer.sqrt(5), "\n"
# output = 2
print "sqrt(6):", Integer.sqrt(6), "\n"
# output = 2

## Output
```ruby
sqrt(4):2
sqrt(5):2
sqrt(6):2
```

What is Integer.sqrt() in Ruby?

Returns the largest integer less than or equal to the square root of a non-negative number.