Problem performing 'atan'

[buckbuilt03]

Need atan(x/y);  x = 1e3 ohms.  y = 338.63 ohms.  Theta should equal 18.71 degrees.  coming up with decimal.  I even tried this as well....ratio = x/y;  atan(ratio);  theta = (x/y)/tan.  Help please...no debug errors.

[MrBcx]

Need atan(x/y);  x = 1e3 ohms.  y = 338.63 ohms.  Theta should equal 18.71 degrees.  coming up with decimal.  I even tried this as well....ratio = x/y;  atan(ratio);  theta = (x/y)/tan.  Help please...no debug errors.
[/quote

The only way that theta can equal 18.71 degrees is if you arrange things like this (shown in BASIC)

r2d = 57.2958     ' convert radians to degrees

PRINT atn (338.63 / 1e3) * r2d

[buckbuilt03]

So what you're saying is that C can't perform a binary trig function without prior conversion??  I know how to convert on paper from repetition of the formula but,..........hmmmmmnnnnn, maybe I've been staring at the monitor too long. 
Thanks man...I'll further research your example,

much obliged,

buck

[MrBcx]

#include <math.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
printf("% .15G\n",(double)atan(338.63/1e3)*57.2958);
  return 0;
}

[Stefan Pendl]

In most languages trigonometry is performed in radians, so you need to convert back and forth into degrees.

[Bitbeisser]

In most languages trigonometry is performed in radians, so you need to convert back and forth into degrees.

And the doc/online help clearly state that this is the case for Pelle's C as well:

atan, atanf, atanl functions
 
Purpose:
Computes the arc tangent.

Syntax:
float atanf(float x);
double atan(double x);
long double atanl(long double x);

Declared in:
<math.h>

Description:
The function computes the angle whose tangent is x, in the interval [-pi/2, +pi/2] radians.
 
Returns:
The arc tangent of x.

Ralf