Question

好的，所以我在c ++中创建了一个二次方程求解器，似乎无法在虚数上得到正确的输出。实数根很好（例如x = 2和x = 5）但是当虚数出现时，会出现奇怪的事情（x = -1。＃IND）??有人请帮我解决这个问题吗？我想让它显示更像x = 5.287 * i的东西。这是我的代码

#include <iostream>
#include <string>
#include <cmath>
#include <complex>
using namespace std;
int main() {

    cout << "Project 4 (QUADRATIC EQUATION)\nLong Beach City College \nAuthor: Mathias Pettersson \nJuly 15, 2015\n" << endl;
    cout << "This program will provide solutions for trinomial expressions.\nEXAMPLE: A*x^2 + B*x^2 + C = 0" << endl;

    double a, b, c;
    double discriminant;

    //Variable Inputs
    cout << "Enter the value of a: ";
    cin >> a;
    cout << "Enter the value of b: ";
    cin >> b;
    cout << "Enter the value of c: ";
    cin >> c;

    //Computations
    discriminant = (b*b) - (4 * a * c);
    double x1 = (((-b) + sqrt(discriminant)) / (2 * a));
    double x2 = (((-b) - sqrt(discriminant)) / (2 * a));

    //Output
    if (discriminant == 0)
    {
        cout << "The discriminant is ";
        cout << discriminant << endl;
        cout << "The equation has a single root.\n";
    }
    else if (discriminant < 0)
    {
        cout << "The discriminant is ";
        cout << discriminant << endl;
        cout << "The equation has two complex roots.\n";
        cout << "The roots of the quadratic equation are x = " << x1 << "*i, and" << x2 << "*i" << endl;
    }
    else 
    {
        cout << "The discriminant is ";
        cout << discriminant << endl;
        cout << "The equation has two real roots.\n";
    }

    //Final Root Values
    cout << "The roots of the quadratic equation are x = ";
    cout << x1;
    cout << ", ";
    cout << x2 << endl << endl;
    system("PAUSE");

    return 0;
}

Answer 1

double不代表复数。

而不是将double传递给sqrt：

sqrt(discriminant)

传递complex number以获得复杂的结果：

sqrt(std::complex<double>(discriminant))

c ++二次方程代码输出错误

1 个答案: