# Square Root

One of the more popular `Math` class functions is the square root function. Like the `floor()` and `ceil()` methods, the square root method takes and returns the `double` datatype. It can be written as follows, `Math.sqrt(25)`, and returns the rounded positive square root. Review the examples below.

SquareRootExample.java
``````package exlcode;

public class SquareRootExample {

public static double exampleVariableOne = Math.sqrt(100);
public static double exampleVariableTwo = Math.sqrt(6.25);
public static double exampleVariableThree = Math.sqrt(3);

public static void main(String[] args) {
System.out.println(exampleVariableOne);
System.out.println(exampleVariableTwo);
System.out.println(exampleVariableThree);
}
}``````

This method will return a `double` number even if the result is a perfect square. The error that will occur if we use a number less than zero is a result of "NaN", which stands for "Not a Number". Therefore, if we were to write `Math.sqrt(-4)`, the return will be "NaN". Imaginary numbers cannot be represented or returned using this method. And lastly, keep in mind that this function will only return one positive square root value.

#### Application Question

`Math.sqrt(16)` returns