# Atan2

Computes four-quadrant inverse tangent of elements of two vectors.

## Syntax

Fortran:

call vsatan2( n, a, b, y )

call vdatan2( n, a, b, y )

C:

vsAtan2( n, a, b, y );

vdAtan2( n, a, b, y );

## Input Parameters

Name | Type | Description
--- | --- | ---
n | FORTRAN: INTEGER, INTENT(IN) C: int | Specifies the number of elements to be calculated.
a, b | FORTRAN: REAL, INTENT(IN) for vsatan2 DOUBLE PRECISION, INTENT(IN) for vdatan2 C: const float* for vsAtan2 const double* for vdAtan2 | FORTRAN: Arrays, specify the input vectors a and b. C: Pointers to arrays that contain the input vectors a and b.

## Output Parameters

Name | Type | Description
--- | --- | ---
y | FORTRAN: REAL for vsatan2 DOUBLE PRECISION for vdatan2 C: float* for vsAtan2 double* for vdAtan2 | FORTRAN: Array, specifies the output vector y. C: Pointer to an array that contains the output vector y.

## Description

The elements of the output vector y are computed as the four-quadrant arctangent of `a[i] /b[i]`.

Parent topic: Trigonometric Functions