c语言如何运用输入输出流计算

Question

Answer 1

第几题？
3.

#include <stdio.h>
#include <math.h>
int main()
{
    int a,b;
    double c,ar;
    scanf("%d %d",&a,&b);
    c = sqrt((double)a*a+b*b);
    ar = (double)a*b/2;
    printf("第三边长:%g，面积:%g",c,ar);
    return 0;
}

4.

#include <stdio.h>
int main()
{
    double a,s;
    scanf("%lf",&a);
    s = a*50*0.9;
    printf("税后所得:lf",s);
    return 0;
}