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Thread: main calls Math.cos and myCos twice.....

  1. #1
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    Default main calls Math.cos and myCos twice.....

    Task: a program that calls Math.cos and myCos twice, once passing Math.PI another passing Math.PI/6.0

    myCos should compute and return the value of

    1.0 - x^2/(2!) + x^4/(4!) - x^6/(6!) + ... + x^96/(96!) - x^98/(98!)



    import java.util.Scanner;
    class Cos
    {
        double x;
        double sum = 0.0;
        double count= 2.0;
        double term= 1.0;
        double sign = 1.0;
        Scanner kb = new Scanner(System.in);
        System.out.println("Enter number of term to sum:");
     
       while (count <= 98)
        {
            sum = sum + sign* 1.0/term;
            sign = -sign;
            sum= count*(count-1)*sum;
            term = term*x*x;
            count ++;
            double y= Math.pow(X4);
        }
     
        System.out.println("Math.cos =" +Math.cos);
        System.out.println("myCos=" +sum)
    }


  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: main calls Math.cos and myCos twice.....

    You don't have your code inside of a method.

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    Default Re: main calls Math.cos and myCos twice.....

    Oh, yes thank you! I believe my formula is not correct and that's my main problem. I don't understand how to formulate all the things that is asked for in this code.

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    Default Re: main calls Math.cos and myCos twice.....

    I need help!!!!! I spent the whole day working on this, that's how bad I am.

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    Super Moderator Norm's Avatar
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    Default Re: main calls Math.cos and myCos twice.....

    Hard to help you with code when we can't see the code.
    If you post any code please explain what your problems are.

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    Default Re: main calls Math.cos and myCos twice.....

    public class Cos
    {
        public static void main(String[] args)
        {
            // your code goes here
        }
    }

    If you are unsure of the Java syntax, I would recommend reading The Java Tutorials, starting with Getting Started and the Learning the Java Language sections.

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    Default Re: main calls Math.cos and myCos twice.....

    Thank you for your help. Now I have this and I still have a problem with the factorial.....
    import java.math.BigInteger;
    import java.util.Scanner;
    class Cos
    {
        public static void main(String[] args)
        {
           double sum = 0.0;
           int f = 2, count = 1, sign = 1, n=0, numberTerms;
           BigInteger factorial = BigInteger.ONE;
           for (double i=1.0; i<=98; i++)
           {
               factorial=factorial.multiply(BigInteger.valueOf(long));
           }
     
           Scanner kb = new Scanner(System.in);
     
           System.out.println("Enter number of terms to sum:");
           numberTerms.kb.nextInt();
     
           while (count <= numberTerms)
           {
               sum = sum + sign * Math.pow(kb,n)/factorial;
               sign = -sign;
               factorial = factorial+2;
               n = n+2;
               count++;
           }
     
           System.out.println("Mycos = " +sum);
           System.out.println("Math.cos =" +Math.cos);
        }  
    }


    when trying to compile, it says class is expected in
    factorial=factorial.multiply(BigInteger.valueOf(long));

  8. #8
    Super Moderator Norm's Avatar
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    Default Re: main calls Math.cos and myCos twice.....

    it says class is expected in
    Please post the full text of the error message.

    "long" is a keyword not a variable. Create and Use a variable for the valueOf argument.

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    Default Re: main calls Math.cos and myCos twice.....

    O.K. So, now it compiles.... but it's not right. I believe it's my equation. =_= I don't know what to do.... I can't believe I have been doing this problem for a week now.... I need a book... Please help me >.<


    import java.util.Scanner;
    class Cos
    {
        public static void main(String[] args)
        {
           double sum = 0.0;
           double count = 1, sign = 1, d=0, numberTerms=98;
           double n = 3;
           double f = n;
           for(double p = (n - 1); p > 1; p--)
           {
               f = f * p;
           }
     
           Scanner input = new Scanner(System.in);
           System.out.println("Enter number of terms to sum:");
           double kb = input.nextDouble();
     
           while (count <= numberTerms)
           {
               double t= Math.pow(kb,d);
               sum = (sum + sign * t)/f;
               sign = -sign;
               d = d+2;
               count++;
           }
     
           System.out.println("Mycos = " +sum);
           System.out.println("Math.cos =" +Math.PI/6.0);
           System.out.println("Math.cos =" +Math.PI);
        }  
    }

  10. #10
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    Default Re: main calls Math.cos and myCos twice.....

    Correction!

     System.out.println("Mycos = " +sum);
           System.out.println("Math.cos =" +Math.cos(Math.PI/6.0));
           System.out.println("Math.cos =" +Math.cos(Math.PI));

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    Default Re: main calls Math.cos and myCos twice.....

    Is everything solved?

  12. #12
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    Default Re: main calls Math.cos and myCos twice.....

    Nope, I believe my factorial is wrong but I don't know how to correct it....

  13. #13
    Super Moderator Norm's Avatar
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    Default Re: main calls Math.cos and myCos twice.....

    my factorial is wrong
    Can you do the steps manually and get the correct answer and then compare that with what the program does when you step thru it statement by statement.
    Can you write a small test program that does just the factorial function and get that to work?

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