求问这个程序错误
#include <stdio.h>main()
{
float r,l,s;
float pi=3.1415926;
printf("请输入圆的半径r=");
sacnf("%f",&r);
l=2*pi*r;
s=pi*r*r;
printf("圆的周长=6.2%f，圆的面积=6.2%f",l,s);
return 0;
}
问一下为什么会出现这个错误 7 undefined reference to `sacnf'
[Error] ld returned 1 exit status
