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# StrictMath acos() Method in Java

• Last Updated : 19 Jul, 2018

The java.lang.StrictMath.acos() is an inbuilt method which returns cosine of a given argument and an angle. The angle which is returned is within the range between 0.0 and pi.
Note: If the absolute value of the argument is greater than 1 or the argument is itself a NaN then the result is also NaN.

Syntax:

`public static double acos(double num)`

Parameters: The method accepts one parameter num which is of double type and refers the arc whose cosine is to be returned.

Return Value: The method returns the arc cosine of the argument.

Examples :

```Input: num = 0.45
Output: 1.1040309877476002

Input: num = 8.9
Output: NAN
```

Below programs illustrate the java.lang.StrictMath.acos() method:
Program 1: For positive number

 `// Java program to illustrate the``// java.lang.StrictMath.acos()``import` `java.lang.*;`` ` `public` `class` `Geeks {`` ` `    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``double` `num1 = ``0.65``, num2 = ``6.30``;`` ` `        ``// It returns the arc cosine of a value``        ``double` `acosValue = StrictMath.acos(num1);``        ``System.out.println(``"The arc cosine value of "``+``                             ``num1 + ``" = "` `+ acosValue);`` ` `        ``acosValue = StrictMath.acos(num2);``        ``System.out.println(``"arc cosine value of "``+``                             ``num2 + ``" = "` `+ acosValue);``    ``}``}`
Output:
```The arc cosine value of 0.65 = 0.863211890069541
arc cosine value of 6.3 = NaN
```

Program 2: For negative number.

 `// Java program to illustrate the``// java.lang.StrictMath.acos()``import` `java.lang.*;`` ` `public` `class` `Geeks {`` ` `    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``double` `num1 = -``0.65``, num2 = -``6.30``;`` ` `        ``// It returns the arc cosine of a value``        ``double` `acosValue = StrictMath.acos(num1);``        ``System.out.println(``"The arc cosine value of "``+``                             ``num1 + ``" = "` `+ acosValue);`` ` `        ``acosValue = StrictMath.acos(num2);``        ``System.out.println(``"arc cosine value of "``+``                             ``num2 + ``" = "` `+ acosValue);``    ``}``}`
Output:
```The arc cosine value of -0.65 = 2.278380763520252
arc cosine value of -6.3 = NaN
```

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