实验4

1.题目描述

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
    for(int i=3;i<=400;i++){
        int s=0;
        for(int j=1;j<i;j++){
            if(!(i%j))    s+=j;
        }
        int t=0;
        for(int j=1;j<s;j++){
            if(!(s%j))    t+=j;
        }
        if(s==t)    cout<<i<<" "<<s<<endl;
    }
    return 0;
}

 

2.题目描述

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
    double n=1.0,m=2.0,k,ans=0.0;
    int s;
    cin>>s;
    for(int i=1;i<=s;i++){
        ans+=double(m/n);
        k=n+m;
        n=m;
        m=k;
    }
    cout<<ans<<endl;
    return 0;
}

 

3.题目描述

 

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
    double x,t=0.0,s=0.0,u=1.0,d=1.0,c=1.0;    
    cin>>x;
    while(fabs(u/d)>1e-6){
        s+=c*(u/d);
        c=-c;
        t++,d*=t,t++,d*=t;
        u*=(x*x);
    }
    printf("%.6lf\n",s);
    return 0;
}

 

 4.题目描述

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
    double L=0.0,R=1.57089;
    while(1){
        double mid=(L+R)/2.0;
        if(double(fabs(cos(mid/2.0)-sin(mid)))<1e-6){
            printf("%.6lf\n",mid);
            break;
        }
        else if((cos(mid/2)-sin(mid))>0)    L=mid;
        else R=mid;
    }
    return 0;
}