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Thread: How to handle quadratic roots that don't exist?

  1. #1
    Junior Member kairojya's Avatar
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    Default How to handle quadratic roots that don't exist?

    Hi guys, I'm a new Computer Science major and taking a Java class this semester. I'm unsure about 1 part of an assignment I've been working on. I need to display a few strings in the event that the roots to a quadratic equation do not exist. I'm wondering how to go about doing this.

    From what a know if a value doesn't exist the program would return a value of "NaN", is that correct? However in the NetBeans IDE I'm not able to set and if statement such as:

    if(n > 0){
     
                double discriminant;
                double root1;
                double root2;
     
                discriminant = Math.sqrt(b*b-4*a*c);
                root1 = (-b + discriminant)/(2*a);
                root2 = (-b - discriminant)/(2*a);
     
                PrintWriter out = new PrintWriter(new FileWriter("results.dat", true));
     
                out.println("Root1: " + root1 + ", Root2: " + root2);
                out.close();
     
                if(root1 = NaN, root2 = NaN) {
                    System.out.println("Quadratic equation with the following coefficients:");
                    System.out.println("a: " + a + ";" + " b: " + b + ";" + " c: " + c + ";");
                    System.out.println("has the following roots: " + root1 + " and " + root2);
                }
            }

    As you can see, what I'm wondering how to accomplish is the nested If statement down at the bottom. Int "n" is a number entered into the command line when running the App. Variables a, b, c are doubles asked from the user.

    One other part I'm confused on is how to specify one parameter or the other in the IF statement, as I wrote:

    if(root1 = NaN, root2 = NaN)


    Thanks for the help!

    EDIT: The strings we're copied from a previous assignment and we'll be changed later to display different information, such as "The quadratic equation has non-real roots." or something along those lines. Sorry for the confusion.
    Last edited by kairojya; October 27th, 2009 at 04:49 PM.


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    Junior Member kairojya's Avatar
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    Default Re: How to handle quadratic roots that don't exist?

    Got some help with this issue elsewhere, just going to post my findings in case anyone brings this thread up in a search:

    if(n > 0){
     
                double discriminant;
                double root1;
                double root2;            
     
                discriminant = Math.sqrt(b*b-4*a*c);
                root1 = (-b + discriminant)/(2*a);
                root2 = (-b - discriminant)/(2*a);
     
                PrintWriter out = new PrintWriter(new FileWriter("results.dat", true));
     
                out.println("Root1: " + root1 + ", Root2: " + root2);
                out.close();  // Closing a file after writing to it.
     
                boolean b1 = Double.isNaN(root1);
                boolean b2 = Double.isNaN(root2);
     
                if(b1 || b2) {
                    System.out.println("Quadratic equation with the following coefficients:");
                    System.out.println("a: " + a + ";" + " b: " + b + ";" + " c: " + c + ";");
                    System.out.println("has roots that don't exist.");
                }
    }

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