为什么输出总是4.000000

Question

#include<stdio.h>

int main()
{ double x;
double y=0;
scanf("lf",&x);
if(x<0) y=(abs(x))/2;
else if(x<10) y=3+exp(x);
else if(x<20) y=log10(x);
else if(x<30) y=pow(x,1.5);
else if(x<50) y=(sqrt(x))-1;
else y=3*cos(x);

printf("%f",y);
return 0;

}

Answer 1

scanf语句中应该是%lf，少了%