Format
#include <math.h> double acos(double x);
Language Level: ANSI, POSIX, XPG4
acos calculates the arccosine of x, expressed in
radians, in the range 0 to PI.
Return Value
acos returns the arccosine of x. The value of
x must be between -1 and 1 inclusive. If x
is less than -1 or greater than 1, acos sets errno to EDOM and
returns 0.
Example
This example prompts for a value for x. It
prints an error message if x is greater than 1 or less
than -1; otherwise, it assigns the arccosine of x to y.
#include <stdlib.h> #include <math.h>
#define MAX 1.0 #define MIN -1.0
int main(void)
{
double x, y;
printf( "Enter x\n" ); scanf( "%lf", &x );
/* Output error if not in range */
if ( x > MAX )
printf( "Error: %lf too large for acos\n", x );
else
if ( x < MIN )
printf("Error: %If too small for acos\n",x);
else {
y = acos(x);
printf("acos(%If) = %If\n", x, y);
}
return 0;
/************************************************
For the following input: 0.4
The output should be:
Enter x
acos(0.400000) = 1.159279
************************************************/
}
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asin -- Calculate Arcsine
atan - atan2 -- Calculate Arctangent
cos -- Calculate Cosine
cosh -- Calculate Hyperbolic Cosine
_facos -- Calculate Arccosine
_fcos -- Calculate Cosine
_fcossin -- Calculate Cosine and Sine
_fsincos -- Calculate Sine and Cosine
sin -- Calculate Sine
sinh -- Calculate Hyperbolic Sine
tan -- Calculate Tangent
tanh -- Calculate Hyperbolic Tangent
<math.h>