Message-ID:	<386AF6BF.EEBC8910@earthlink.net>
From:	Martin Ambuhl <mambuhl AT earthlink DOT net>
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Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Inverse trigonometry functions in Djgpp
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Date:	Thu, 30 Dec 1999 06:07:07 GMT
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"Jarkko Kähkönen" wrote:
> 
> Atan () - don't work!
> Here is a bit of my code:
> 
> float direction;
> 
> direction = atan ( 120 / 90 );
> printf ("%f", direction");
> 
> And output is this:
> 0.927295
> 
> But with calculator it is:
> tan^-1 (120 / 90) = 53.1301023...
> 
> Is atan () right inverse tan function?

Yes, although atan2() is more general:

#include <math.h>
#include <stdio.h>
#include <float.h>
int main(void)
{
    double direction, degrees;
    direction = atan(120. / 90);
    degrees = direction * 180 / M_PI;
    printf("atan(120./90) = %*g in radian measure\n"
           "               (%*g degrees)\n"
           "What's the problem?\n",
           DBL_DIG + 2, direction, DBL_DIG + 2, degrees);
    return 0;
}


atan(120./90) =          0.927295 in radian measure
               (          53.1301 degrees)
What's the problem?




-- 
Martin Ambuhl	mambuhl AT earthlink DOT net

What one knows is, in youth, of little moment; they know enough who
know how to learn. - Henry Adams

A thick skin is a gift from God. - Konrad Adenauer
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