Java Math.acos() method

The java.lang.Math.acos() is used to calculate the trigonometric Arc Cosine of an angle. Arc cosine is also called as inverse of a cosine. This method returns the values between 0.0 and pi.

Syntax

Parameter

Return

If the argument is positive or negative number, this method will return the Arc cosine value.
If the argument is NaN or outside the range -1 and 1, this method will return NaN.

Example 1

public class AcosExample1
{
    public static void main(String[] args) 
    {
        double a = 1.0;
        System.out.println(Math.acos(a));
    }
}

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Output:

0.0

Example 2

public class AcosExample2
{
    public static void main(String[] args) 
    {
        double a = -1.0;
        System.out.println(Math.acos(a));
    }
}

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Output:

3.141592653589793

Example 3

public class AcosExample3
{
    public static void main(String[] args) 
    {
        double a = 1.380;
        // value of a is greater than 1 so Output is NaN
        System.out.println(Math.acos(a));
    }
}

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Output:

NaN

Example 4

public class AcosExample4
{
    public static void main(String[] args) 
    {
        double a = Math.PI;
        // return NaN because Math.PI value is 3.414 that is greater than 1
        System.out.println(Math.acos(a));
    }
}

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Output:

NaN

Example 5

public class AcosExample5
{
    public static void main(String[] args) 
    {
        double a = Math.PI;
        double b = Math.toRadians(a);
        System.out.println(Math.acos(b));
    }
}

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Output: