c++头文件 #include<iostream>

cout<<"C1="<<setiosflags(ios::fixed)<<setprecision(2)<<3.14*r*2<<endl;
cout<<"Sa="<<setiosflags(ios::fixed)<<setprecision(2)<<3.14*r*r<<endl;
cout<<"Sb="<<setiosflags(ios::fixed)<<setprecision(2)<<4*3.14*r*r<<endl;
cout<<"Va="<<setiosflags(ios::fixed)<<setprecision(2)<<(4*3.14)/(3*r*r*r)<<endl;
cout<<"Vb="<<setiosflags(ios::fixed)<<setprecision(2)<<3.14*r*r*h<<endl;

输出小数点后两位