在C中找到局部最大值

| 我想在此Sin（x）函数的0到3.1416的区间内找到局部最大值。但它始终显示0作为最大值。即最大值= 0;请帮助我发现我的缺点。谢谢。

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#ifndef max
    #define max(a,b) ((a)>(b)?(a):(b))
#endif
double f(double x){
return sin(x);
}
double bisection(double a,double b)
{
double Fa=f(a);
double Fb=f(b);
double midpoint=(a+b)/2;
double Fmidpoint=f(midpoint);
while(abs(b-a)>1e-6){
double left=(a+midpoint)/2;
double right=(b+midpoint)/2;
double Fleft=f(left);
double Fright=f(right);
if(midpoint>max(Fleft,Fright)){
    a=left;
    Fa=Fleft;
    b=right;
    Fb=Fright;
}
else{
    if(Fleft>Fright)
    {
        b=midpoint;
        Fb=Fmidpoint;
        midpoint=left;
        Fmidpoint=Fleft;
    }
    else{
        a=midpoint;
        Fa=Fmidpoint;
        midpoint=right;
        Fmidpoint=Fright;
    }
}
}
return midpoint;
}
int main(){
double maximum;
double rangeleft=0;
double rangeright=3.1416;
maximum=bisection(rangeleft,rangeright);
printf(\"%d\",maximum);
return 0;
}