From:	"Jarkko Kähkönen" <jarkko DOT kahkonen AT mbnet DOT fi>
Newsgroups:	comp.os.msdos.djgpp
References:	<wKza4.591$eq DOT 7079 AT uutiset DOT nic DOT fi> <386AF6BF DOT EEBC8910 AT earthlink DOT net>
Subject:	Re: Inverse trigonometry functions in Djgpp
Lines:	50
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Message-ID:	<hwHa4.613$eq.7331@uutiset.nic.fi>
Date:	Thu, 30 Dec 1999 13:41:03 +0200
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

>
>
>"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?
>
>
>
>

Thanks to everybody for solving my problem!

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