#include
#include
main()
    {
    double x,s;
   
    printf("input number:\n");
   
    scanf("%lf",&x);

    s=sin(x);
   
    printf("sine of %lf is %lf\n",x,s);
    }

[Error] C:\Users\Administrator\Documents\C-Free\Temp\未命名1.cpp:11: error: `sin' was not declared in this scope

这是怎么回事啊   第一次求教

谢谢，编译通过