no.8.c

中南大学C语言程序设计实习 1 实验一：C语言图形模式的设置 2 实习二：一元函数的图形绘制 3 实习三：二维图形的几何变换 4 实习四：非线性方程求根的二分法 5 实习五

#include "stdio.h"
#include "conio.h"

#define ROOT1_PRECISION 10e-4
#define ROOT2_PRECISION 10e-3
#define PI 3.1415926


float x1(float x)
{
    return x;
}    

float x2(float x)
{
    return ( ( 2 * x) / ( 1 - x) );
}

float ln(float (*x)(float a), float a, float precision, int* n)
{
    int flag = 1;
    int i = 0;
    float fx = 1;
    float t = x(a);
    float s = 0;
    
    while ( t > precision ) {
        i++;
        fx = fx * x(a);
        t = fx / i;
        s = s + flag * t;
        flag = - flag;    
    }    
    *n = i;
    return s;
}

float ex(float (*x)(float a), float a, float precision)
{
    float fx = 1;
    float fy = 1;
    float i = 0;
    float t = 1;
    float s = 1;
    
    while ( t > precision ) {
        i++;
        fy = fy * i;
        fx = fx * x(a);
        t = fx / fy;
        s = s + t;
    }
    return s;
}

int main()
{
    float s;
    int n;
    float x;
    s = ln(x1, 1, ROOT1_PRECISION, &n);
    printf("ln(1+x) ln2 = %.4f you should compute %d times.\n", s, n);
    s = ln(x2, 1.0 / 3, ROOT1_PRECISION, &n);
    printf("ln((1+x)/(1-x)) ln2 = %.4f you should compute %d times.\n", s, n);
    printf("Input x:");
    scanf("%f", &x);
    s = ex(x1, x, ROOT2_PRECISION);
    printf("e(x=%.0f) = %.3f", x, s);
    getch();
}