whats wrong with this? no errors but wrong result

Code:

#include <stdio.h>
#include <math.h>
main()
{
	double x;

	x =45.0; /* 45 degree */
	x *= 3.141593 /180.0; /* convert to radians*/

	printf("The sine of 45 is:	 %f.\n", sin);
	printf("The cosine of 45 is:	 %f.\n", cos);
	printf("The tangent of 45 is:	 %f.\n", tan);
	return 0;
}

i get no errors whatsoever but the output is only 0's, whats wrong with this?

Probably because you aren't calling sin, cos and tan functions. You're just using the name of them. (Which is effectively a pointer to the function itself, not invoking it.) Turn on your compiler's warnings and pay attention to them. It should be freaking out.

Quzah.

try sin(x) cos(x) tan(x)

You must have warnings turned off when you compile.

do you mean this?

Code:

--Configuration: trig - Win32 Debug--------------------
Compiling...
trig.c

trig.obj - 0 error(s), 0 warning(s)

edit: i fixed it.

Code:

#include <stdio.h>
#include <math.h>
main()
{
	double x;

	x =45.0; /* 45 degree */
	x *= 3.141593 /180.0; /* convert to radians*/

	printf("The sine of 45 is:	 %f.\n", sin(x));
	printf("The cosine of 45 is:	 %f.\n", cos(x));
	printf("The tangent of 45 is:	 %f.\n", tan(x));
	return 0;
}

i guess those that published the book run out of ink in this part of the code eheh

Yes. Turn your compiler's warnings on. You will get a bunch. See?

Code:

freakout.c:4: warning: return type defaults to `int'
freakout.c: In function `main':
freakout.c:10: warning: double format, pointer arg (arg 2)
freakout.c:11: warning: double format, pointer arg (arg 2)
freakout.c:12: warning: double format, pointer arg (arg 2)

Quzah.

Originally Posted by InvariantLoop

Code:

 
    x *= 3.141593 /180.0; /* convert to radians*/

If you are going to be doing math, you might as well get the best precision that you can. Doubles are good for 15 or 16 significant decimal digits, but not if your approximation of pi is only 8 digits:

Code:

#include <stdio.h>
#include <math.h>
int main()
{
    double x;
    double pi;

    x =45.0; /* 45 degree */
    x *= 3.141593 /180.0; /* convert to radians*/

    printf("First with pi = 3.141593:\n");
    printf("  The sine of 45 degrees is:    %.15f\n", sin(x));
    printf("  The cosine of 45 degrees is:  %.15f\n", cos(x));
    printf("  The tangent of 45 degrees is: %.15f\n", tan(x));

    /* 
     * Here's a way to get the best precision pi that your library can
     * calculate, without typing in a bunch of digits:
     *
     */

    pi = 4.0 * atan(1.0);

    x = 45.0;
    x *= pi / 180.0;
    printf("\n\n");
    printf("Now, with pi = %.15f:\n", pi);
    printf("  The sine of 45 degrees is:    %.15f\n", sin(x));
    printf("  The cosine of 45 degrees is:  %.15f\n", cos(x));
    printf("  The tangent of 45 degrees is: %.15f\n", tan(x));

    return 0;
}

Regards,

Dave

> --Configuration: trig - Win32 Debug--------------------
Then goto your project settings->compiler
Find the warning level and set it to 4
Then see if it complains about your code.

Of course, the better option would be to get gcc, which as well as being a more compliant compiler than VC6, it also has many more diagnostics (in particular it can tell you when you're making a mess of printf as Quzah points out).