The asin() method of java.lang.Math class, computes the arc sine also called as an inverse of a sine of a given value. This method is useful when we have the sine of an angle and we need to find the angle. This method returns the arc sine of an angle in between -pi/2 and pi/2.

• If the argument is NaN or its absolute value is greater than 1, then the result is NaN.
• If the argument is zero, then the result is a zero with the same sign as the argument.

Syntax of Math asin() Method

public static double asin(double angle)

• Parameter: angle: The value whose arc sine is to be returned.
• Return: The arc sine of the argument in radians.
• Valid Range: -1.0 <= angle <= 1.0 and the values outside this range will result NaN.

Important Points:

• The valid input returns a real angle between -pi/2 and pi/2.
• The zero input produces 0.0.
• asin(1.0) is equals to pi/2 and asin(-1.0) is equals to -pi/2.
• The invalid input returns NaN to indicate an error.

Examples of Java Math asin() Method

Example 1: In this example, we will try to handle out of valid range values.

// Java program to handle out-of-range input
public class Geeks {
    
    public static void main(String[] args) {
        
        double i = 2.0; 
        System.out.println("asin(" + i + ") = " + Math.asin(i));
    }
}

asin(2.0) = NaN

Explanation: Here, 2.0 is not a valid sine value, so asin() indicates the error with NaN.

Example 2: In this example, we will convert the degrees to radians before asin().

// Java program to convert degrees to radians
public class Geeks {
    
    public static void main(String[] args) {
        
        double degrees = 30.0;                    
        double radians = Math.toRadians(degrees); 
        System.out.println("asin(sin30°) in radians: "
            + Math.asin(Math.sin(radians)));
    }
}

asin(sin30°) in radians: 0.5235987755982988

Example 3: In this example, we will take multiple inputs in one array.

// Java program to loop through multiple values
public class Geeks {
    
    public static void main(String[] args) {
        
        double[] values = {1.0, 0.0, -1.0, 0.5};
        for (double v : values) {
            System.out.printf("asin(%.1f): %.4f rad\n", v, Math.asin(v));
        }
    }
}