求值 -arccos(-1)

这个不是有函数的吗?

例子:

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

void main( void )
{
double x, y;

printf( "Enter a real number between -1 and 1: " );
scanf( "%lf", &x );
y = asin( x );
printf( "Arcsine of %f = %f\n", x, y );
y = acos( x );
printf( "Arccosine of %f = %f\n", x, y );
}