Manual Reference Pages - atan2 (3)
atan2(3f) - [FORTRAN:INTRINSIC:TRIGONOMETRIC] Arctangent function
CONTENTS
Syntax
Description
Arguments
Return Value
Example
Standard
Class
SYNTAX
result = atan2(y, x)
DESCRIPTION
atan2(y, x) computes the arctangent of the complex number
X + i Y.This function can be used to transform from Cartesian into polar coordinates and allows to determine the angle in the correct quadrant. To convert from Cartesian Coordinates (x,y) to polar coordinates
(r,theta): $$ \begin{aligned} r &= \sqrt{x**2 + y**2} \\ \theta &= \tan**{-1}(y / x) \end{aligned} $$
ARGUMENTS
Y - The type shall be REAL. X - The type and kind type parameter shall be the same as Y. If Y is zero, then X must be nonzero.
RETURN VALUE
The return value has the same type and kind type parameter as Y. It is the principal value of the complex number (X + i, Y). If X is nonzero, then it lies in the range -PI <= atan(x) <= PI. The sign is positive if Y is positive. If Y is zero, then the return value is zero if X is strictly positive, PI if X is negative and Y is positive zero (or the processor does not handle signed zeros), and -PI if X is negative and Y is negative zero. Finally, if X is zero, then the magnitude of the result is PI/2.
EXAMPLE
Sample program:
program demo_atan2 real(4) :: x = 1.e0_4, y = 0.5e0_4 x = atan2(y,x) end program demo_atan2
STANDARD
[[FORTRAN 77]] and later
CLASS
[[Elemental procedure|Elemental function]]
| atan2 (3) | March 18, 2019 |
