查找多项式的 y、导数和积分值的程序（已更新）

Question

制作一个应该计算多项式 y 值导数和积分的程序...现在在格式化 for 循环时遇到问题，因此它循环遍历我想要的所有 x 值（由用户确定）。

很确定数学函数现在也不是完全正确的，但是一旦我让这个循环工作，我可以稍后再去处理它们哈哈

这是我的代码：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void explain();
void math(double a, double b, double c, double x, double xi, double *fx, double *fD, double *A);

int main()
{
    double a, b, c;
    double xi, xf, xc, x=0;
    double fx=0, fD=0, A=0;

    printf("SECOND DEGREE POLYNOMIAL CALCULATOR\n\n");
    explain();

    printf("\n\nEnter a value for a: ");
    scanf("%lg", &a);
    printf("Enter a value for b: ");
    scanf("%lg", &b);
    printf("Enter a value for c: ");
    scanf("%lg", &c);

    printf("\nYour function is %lgx^2%+-lgx%+-lg", a, b, c);

    printf("\n\nEnter your initial x-value: ");
    scanf("%lg", &xi);
    printf("Enter your final x-value: ");
    scanf("%lg", &xf);
    printf("Enter what you would like to increment by: ");
    scanf("%lg", &xc);

    printf("|   x   |   f(x)   |   f'(x)   |   A   |\n"); //printing table
    printf("----------------------------------------\n");
    for(int i=xi; i<xf; i++) {
        math(a, b, c, x, xi, &fx, &fD, &A);
        printf("| %.3lf | %.3lf | %.3lf | %.3lf |\n", x, fx, fD, A);
        x = x + xc;
    }

    return;
}
void explain() {
    printf("This program computes the integral and derivative of a user inputted second-degree polynomial (f(x)=ax^2+bx+c).\n");
    printf("You will be asked to enter the 3 coefficients of your polynomial, followed by your initial x-value, your\n");
    printf("final x-value, and the increment value between each x.");
}
void math(double a, double b, double c, double x, double xi, double *fx, double *fD, double *A) {
    *fx = (a*(x*x)) + (b*x) + c;  //finding y values
    *fD = (2*a) + b;   //finding derivative values
    *A = ((a/3)*pow(x,3) + (a/2)*pow(x,2) + c*x) - ((a/3)*pow(xi,3) + (a/2)*pow(xi,2) + c*xi);  //finding integral values

    return;
}

这是输出的屏幕截图，如您所见，table 仅打印到 1，而不是所需的 5（由输入指示）。我需要更改 for 循环中的内容以使其正确输出，但我不确定该怎么做

Answer 1

我发现你的代码有问题：

1> 你的推导函数不正确。应该是 2*a*x + b

2> 我将 for 循环更改为 while 循环，步骤是从标准输入输入的 xc

这是我的解决方案和你的最新答案：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void explain();
void math(double a, double b, double c, double x, double xi, double *fx, double *fD, double *A);

int main()
{
    double a, b, c;
    double xi, xf, xc, x = 0;
    double fx = 0, fD = 0, A = 0;

    printf("SECOND DEGREE POLYNOMIAL CALCULATOR\n\n");
    explain();

    printf("\n\nEnter a value for a: ");
    scanf("%lg", &a);
    printf("Enter a value for b: ");
    scanf("%lg", &b);
    printf("Enter a value for c: ");
    scanf("%lg", &c);

    printf("\nYour function is %lgx^2%+-lgx%+-lg", a, b, c);

    printf("\n\nEnter your initial x-value: ");
    scanf("%lg", &xi);
    printf("Enter your final x-value: ");
    scanf("%lg", &xf);
    printf("Enter what you would like to increment by: ");
    scanf("%lg", &xc);

    printf("|   x   |   f(x)   |   f'(x)   |   A   |\n"); //printing table
    printf("----------------------------------------\n");

    x = xi;
    double nextX;
    while (x <= xf) {
        nextX = x + xc;
        math(a, b, c, x, nextX, &fx, &fD, &A);
        printf("| %.3lf | %.3lf | %.3lf | %.3lf |\n", x, fx, fD, A);
        x = x + xc;
    }

    return 0;
}
void explain() {
    printf("This program computes the integral and derivative of a user inputted second-degree polynomial (f(x)=ax^2+bx+c).\n");
    printf("You will be asked to enter the 3 coefficients of your polynomial, followed by your initial x-value, your\n");
    printf("final x-value, and the increment value between each x.");
}
void math(double a, double b, double c, double x, double xi, double *fx, double *fD, double *A) {
    *fx = (a*(x*x)) + (b*x) + c;  //finding y values
    *fD = (2 * a * x) + b;   //finding derivative values
    *A = ((a / 3)*pow(x, 3) + (a / 2)*pow(x, 2) + c * x) - ((a / 3)*pow(xi, 3) + (a / 2)*pow(xi, 2) + c * xi);  //finding integral values

    return;
}

查找多项式的 y、导数和积分值的程序（已更新）

Program that finds y, derivative, and integral vals of a polynomial (UPDATED)

c

polynomial-math