# 
##   

The **`atan2()` function** in Java accepts two argument values, `x` and `y`. It computes a radian angle `Θ` in the euclidean plane between the positive x-axis and the ray to the point.

# 
#  Basic formulas

The formulas below can be used to calculate `arctan(y/x)`.

1. `x = rcosθ)`
2. `y = rsin(θ)`
3. `θ = arctan(y/x)` or `atan2()`

# 
#  Syntax

---
```java
double atan2(double y, double x)
```
---

##
## Parameters

It accepts two arguments of the primitive `double` type.

* **`x`**: value on the x-axis named _abscissa_.
* **`y`**: value on the y-axis named _ordinate_.

##
## Return value

The return value is the `Θ` component of the point `(r, Θ)` in polar coordinates corresponding to the point `(x, y)` in the Cartesian plane.
 * `(x, y) ≠ (0, 0)`

# 
## Special cases

* If the argument passed to it is `NaN`, the result will be `NaN`.

* If both x and y arguments are positive infinity, the result will be nearest to `π/4` of the primitive `double` type.

* If both argument values are negative infinity, the result will be nearest to -3*$\frac{pi}{4}$ of the primitive `double` type.

* If the $1^{st}$ argument is positive infinity and the $2^{nd}$ argument is negative infinity, the result will be 3*$\frac{pi}{4}$ of the primitive double type.

* If the $1^{st}$ argument is negative infinity and the $2^{nd}$ argument is positive infinity, the result will be -$\frac{pi}{4}$ of the primitive double type.

# 
## Code

In the code snippet below:
* (0, 0): if the value of _x= 0, y= 0_ ,the angle will be `0`.

* (10, 3): if the value of _x= 10, y= 3_, the angle will be `1.2793395323170296`.

Execute the code below and check the output.

class EdPresso {
    public static void main(String args[]) {
        double x= 0, y= 0;
        System.out.println( "Radian angle Θ in euclidean plane(" + x + "," + y + ")= "  + Math.atan2(x,y));
        
        x= 10; y= 3;
        System.out.println( "Radian angle Θ in euclidean plane(" + x + "," + y + ")= "  + Math.atan2(x,y));
    }
}

Demo

How to use Math atan2(double y, double x) in Java

The atan2() function in Java calculates the arctan(y/x) returning an angle Θ in radians based on x and y coordinates.