求 圆周率

<span style="font-size:24px;">/*
求圆周率
π/4=1-1/3+1/5-1/7+1/9....  直到一项的绝对值小于 10^-6 为止
*/
#include<stdio.h>
float getPI(){
	float PI=0,i=1,k=1;
	while(1/i>=1e-6){
		PI=PI+k/i;
		k=k*(-1);
		i+=2;
	}
	return PI*4;
}
int main(void){
	printf("%.10f\n",getPI());
return 0;
}</span>