atan2 (Function)

This function returns the principal value of the arc tangent of argument a divided by argument b.

The sign of both arguments are taken into account in order to determine the quadrant of the resulting value.

Note: This function works with DOUBLE, but can also work with FLOAT as described in the Floating-point math introductory section.

Input:

A : DOUBLE

Value representing the proportion of the y-coordinate.

B : DOUBLE

Value representing the proportion of the x-coordinate.

Returns: DOUBLE

The arch tangent of the value in radians.

Declaration:

FUNCTION atan2 : DOUBLE;
VAR_INPUT
a : DOUBLE;
b : DOUBLE;
END_VAR;

Example:

INCLUDE rtcu.inc
INCLUDE math.inc
 
PROGRAM test;
VAR
  a : DOUBLE;
END_VAR;
 
a := cos(v:=0.4);
DebugMsg(message:=" cos " + doubleToStr(v := a));
DebugMsg(message:="acos " + doubleToStr(v := acos(v:=a)));
a := sin(v:=0.4);
DebugMsg(message:=" sin " + doubleToStr(v := a));
DebugMsg(message:="asin " + doubleToStr(v := asin(v:=a)));
a := tan(v:=0.4);
DebugMsg(message:=" tan " + doubleToStr(v := a));
DebugMsg(message:="atan " + doubleToStr(v := atan(v:=a)));
a := atan2(a:=10.0, b:= 10.0);
DebugMsg(message:="atan2 " + doubleToStr(v := a));
 
// Output:
//  cos 0.9210609916817709
// acos 0.4000000059604644
//  sin 0.3894183477986018
// asin 0.4000000059604644
//  tan 0.4227932257640837
// atan 0.4000000059604645
// atan2 0.7853981633974483
 
END_PROGRAM;