c二分法求根

#include<stdio.h>#include<math.h>#define pi 3.1415926float f(float x);int main(){ float m,e=pow(2,-5); float a=0,b=1; int k=0; m=(a+b)/2;    while(fabs(b-a)>e)   {    if  (f(b)*f(m)<0)    a=m;    if  (f(a)*f(m)<0)     b=m;    m=(a+b)/2;   k=k+1;}   printf("m=%.5f,k=%d\n",m,k);}float f(float x){  float y;  y=exp(-x)-sin(pi*x/2);  return y;}