cubicequation.java

用于求得方程的解的一个小程序

package MyPakeage;

public class CubicEquation implements t1 {
	double m, n, t, s, x1 = 0, x2 = 0, x3 = 0;

	public void x1() {
		if (m == 0) {
			System.out
					.print("Error Input!\n System will put the equation as a quadratic equation to solve.");
			QuadraticEquation x = new QuadraticEquation();
			x.a = n;
			x.b = t;
			x.c = s;
			x.x1();

		} else {
			double a = n / m;
			double b = t / m;
			double c = s / m;
			double q = (a * a - 3 * b) / 9;
			double r = (2 * a * a * a - 9 * a * b + 27 * c) / 54;
			if (r * r < q * q * q) {
				System.out.println("The equation has three answer:");
				t = Math.acos(r / Math.sqrt(q * q * q));
				x1 = -2 * Math.sqrt(q) * Math.cos(t / 3) - a / 3;
				x2 = -2 * Math.sqrt(q) * Math.cos((t + 2 * Math.PI) / 3) - a
						/ 3;
				x3 = -2 * Math.sqrt(q) * Math.cos((t - 2 * Math.PI) / 3) - a
						/ 3;
				System.out.println("x1=" + x1 + "," + "x2=" + x2 + "," + "x3="
						+ x3);
			} else {
				System.out.println("The equation just has one answer:");
				int sgn = (r >= 0) ? 1 : -1;
				double u = -sgn
						* Math.pow(
								(Math.abs(r) + Math.sqrt(r * r - q * q * q)),
								1. / 3);
				double v = (u != 0) ? q / u : 0;
				x1 = u + v - a / 3;
				System.out.println("x=" + x1);
			}

		}
	}

}