C语言大神，这几个编程题怎么做?

Question

如题所述

Answer 1

#include <stdio.h> 

int main( )

{int i,n,a=1,b=2,c;

double s=0;

for(i=0;i<20;i++)

{s+=(double)a/b;

c=a+b;

a=b;

b=c;

}

printf("%lf\n",s);

return 0;

}

#include <stdio.h> 

#include <math.h> 

int main( )

{int i;

double t=1,x,y=0;

scanf("%lf",&x);

x*=x;

t=1;

for(i=1;fabs(t)>=1e-5;i+=2)

{y+=t;

t*=-x/(i*(i+1));

}

printf("%lf\n",y);

return 0;

}

#include <stdio.h> 

#include <math.h> 

int main( )

{double t=sqrt(2),y=2;

int k,t1;

for(;2/t>=(1+1e-6);)

{y*=2/t;

t=sqrt(2+t);

}

printf("%lf\n",y);

return 0;

}