点build时，。显示出了一个错，不明白求解释
#include <stdio.h>#include <math.h>
void main()
{
double x,s;
printf("input number:\n");
scanf("%lf",&x);
s = sin(x);
printf("sin of %lf is %lf\n",x,s);
}
错误提示-----------------Configuration: cyuyan - Win32 Debug--------------------
Linking...
C语言格式.obj : error LNK2005: _main already defined in C语言。c.obj
Debug/cyuyan.exe : fatal error LNK1169: one or more multiply defined symbols found
执行 link.exe 时出错.
cyuyan.exe - 1 error(s), 0 warning(s)
，还有个问题求您帮忙解决一下。