Home Communities
IT Knowledge
Inspiration
Languages
EN

# Java - Math.asin() method example

0 points
Created by:
395

The `Math.asin` function returns number in radians in the range `-Math.PI/2` to `+Math.PI/2`. The function calculates the inverted sine function value.

``````public class CustomMath {

static double calculateAngle(double a, double h) {
return Math.asin(a / h);
}

public static void main(String[] args) {
/*
|\
| \ h
a |  \
|__*\ <- angle
b
*/

double a, b, h;

// a, b and h build isosceles right triangle
a = 3;
b = a;
h = Math.sqrt(a * a + b * b);
System.out.println( calculateAngle(a, h) ); // 0.7853981633974483 <- ~45 degrees

// a, b and h build half of equilateral triangle
a = 3;
b = a * Math.sqrt(3);
h = Math.sqrt(a * a + b * b);
System.out.println( calculateAngle(a, h) ); // 0.5235987755982989 <- ~30 degrees

// a, b and h are not able to build triangle
a = 3;
b = a;
h = 1;
System.out.println( calculateAngle(a, h) ); // NaN
}
}``````

## 1. Documentation

 Syntax ``````package java.lang; public final class Math { public static double asin(double number) { ... } }`````` Note: Classes in the `java.lang` package are imported automatically, so it is not necessary to do it manually - we use just `Math.asin()` call. Parameters `number` - double value that represents the result of the operation `adjacent / hypotenuse` on the right triangle (primitive value). `number` should be in the range `-1` to `+1`. Result `number` value in radians in the range `-Math.PI/2` to `+Math.PI/2` (primitive value). If the value can not be calculated `NaN` is returned. Description `asin` is a static method that takes only one parameter and returns an approximation of the result of the mathematical function arcsine(x).

## 2. Working with degrees

``````public class CustomMath {

static double calculateAngle(double a, double h) {
double angle = Math.asin(a / h);

return (180 / Math.PI) * angle; // rad to deg conversion
}

public static void main(String[] args) {
/*
|\
| \ h
a |  \
|__*\ <- angle
b
*/

double a, b, h;

// a, b and h build isosceles right triangle
a = 3;
b = a;
h = Math.sqrt(a * a + b * b);
System.out.println( calculateAngle(a, h) ); // ~45 degrees

// a, b and h build half of equilateral triangle
a = 3;
b = a * Math.sqrt(3);
h = Math.sqrt(a * a + b * b);
System.out.println( calculateAngle(a, h) ); // ~30 degrees

// a, b and h are not able to build triangle
a = 3;
b = a;
h = 1;
System.out.println( calculateAngle(a, h) ); // NaN
}
}
``````

## References

1. Inverse trigonometric functions - Wikipedia

Join to our subscribers to be up to date with content, news and offers.