atan2 ( y ; x )
returns the base angle (arctan) of a triangle with the sides X and Y.
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Michael George - Show more from this author
Michael George Consulting
Function definition: (Copy & paste into FileMaker's Edit Custom Function window)
The function atan2(y;x) returns the arctan of y,x with adjustments for the signs of x and y so that the angle returned is the angle of the cartesian point (x,y) in radians.
The commonest use of atan2 is in converting between rectangular and polar co-ordinates. The formula for calculating the *initial* heading for a great-circle route from point A to point B uses atan2.
Please be aware that the parameter order is y,x and not x,y as usual.
|Rouel Fernandez, Mountain View, Ca
Dec 22, 2010
|The above does not give the same results as Microsoft Excel. I use the following, Note the special for x=0 and y=0, I define ATAN2(x,y) = 0:
Let ( [
Case ( x > 0 ; Atan( y / x ) ;
x < 0 ; If ( y ≥ 0 ; Pi + Atan ( y / x) ; -Pi + Atan ( y / x)) ;
x = 0 ; If ( y > 0 ; Pi / 2 ; If ( y < 0 ; -Pi / 2 ; 0) )) ;
Convert from 0 to 2*pi: result = mod ( 2* pi + a ; 2 * pi)
|Michael George, Michael George Consulting
Sep 28, 2013
|Excel has the two parameters reversed:
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