Quad project suggestion

[verdell32]

I just had a question before I get started with my third from the last project; I wanted to know are there any threads that could help me with this project?

CSIS 121 Introduction to Computer Science

Project QUAD



Write a program that calculates the two real roots of a quadratic equation of the form:



Ax2 + Bx + C = 0



Where:
A is the coefficient of the squared term,
B is the coefficient of the linear term and
C is the coefficient of the constant term.



The quadratic formula can be used to calculate the two real roots. It follows:
_________
Root = -b ± Ö b2 – 4ac

_____________

2a
Note: the O with the periods over it is a symbol that looks like a check mark


Some sets of data for A, B and C may cause runtime errors.

The program should deal with the fact that we cannot take the square root of a negative number and we can not divide by 0.



A first algorithm for the program:

Get coefficientA, coefficientB and coefficientC from the user

If coefficientA == 0 then

Display “Coefficient of A must not be 0. This is not a quadratic equation.”

else

Calculate the discriminant

If discriminant < 0 then

Display the message “This quadratic does not have real roots,” and end

else

Calculate Root1

Calculate Root2

Display Root1

Display Root2

endif

endif
To turn in your assignment, leave a copy of your work on your login drive(M:\) in a folder called QUAD. I need the source code file QUAD.CPP and the executable file called QUAD.EXE.

[Valmont]

Write a simple main and calculate x1 and x2. Keep it simple.

Question:
` What can you say about accuracy?
` When does it typically occur?

Try this, give me your thoughts, then we move on.

[verdell32]

This is what I have so far; I pretty sure that if you read my above post you can see what I am doing wrong.

// Program Documentation //////////////////////////////////////////////////////
//
// Project Name  : QUAD
//
// Source File   : quad.cpp
//
// Programmed By : 
//
// Last Revision : 12/4/2004
//
// Version Number: 0.1
//
// Program Description ////////////////////////////////////////////////////////
//
// This program will calculate the two real roots of a quadratic equation
// of the form.
///////////////////////////////////////////////////////////////////////////////

// Include Files //////////////////////////////////////////////////////////////
#include <iostream.h>
#include <conio.h>
#include <iomanip.h>
#include <fstream.h>
#include <math.h>

// Function Prototypes ////////////////////////////////////////////////////////

// Program Mainline ///////////////////////////////////////////////////////////

int main( )
{
   double root1;
   double root2;
   double coefficientA = 3;
   double coefficientB = 2;
   double coefficientC = 4;

   //Enter Information
   cout << "Enter coefficient a:";
   cin >> coefficientA;

   cout << "Enter coefficient b:";
   cin >> coefficientB;

   cout << "Enter coefficient c:";
   cin >> coefficientC;

   //Caculations
   root1 = coefficientB * coefficientB - 4 - coefficientA * coefficientC;
   root2 = coefficientB * coefficientB - 4 - coefficientA * coefficientC;

   if ( 2 >= 0 ) {
      coefficientA = coefficientB;

   }else{
      if ( coeffientA == '0' ) {
         coefficientC = coefficientA * 3;

   }//endif
   }//endif
   cout << "Root 1 is: " << setw(8) << root1 << endl;
   cout << "Root 2 is: " << setw(8) << root2 << endl;

   getch();
   return 0;
}//endmn

[Valmont]

Besides the errors, I am not intersested in the if's and else's. Nevermind that. Just implement a plain formula, to get things working quickly.

I have asked you two questions (typed in italics). Try to answer them. Then we move on.
The formula's are:

-b-sqrt(b^2 - 4ac)
-------------------
        2a

-b+sqrt(b^2 - 4ac)
-------------------
        2a

[verdell32]

I new I know that accuracy takes a lot of trail and error before you get it right.
and for the second question I don't know how to exactly answer that question.

For the if/else statements it is required by my professor for this project in Borland C++ 6.

I am down to the last minutes of this project because it is due tomorrow by 12pm.

The program works but, I don't know if its giving the right answer that he is looking for?

Are you telling me to include this line of code to see if it works correctly with what I have already?

[Valmont]

I got home too late. Sorry. You could have learned interesting things.

[verdell32]

He gave us two extra days to make any corrections; if you get anytime to help me, I would appreciate it.

Thanks.

[Valmont]

#include <iostream>
#include <string>
#include <climits>
#include <cmath>

using std::cin;
using std::cout;
using std::endl;
using std::numeric_limits;
using std::streamsize;
using std::string;

//Optional function: depends on IDE. Remove if not needed.
void wait_for_enter();

//Additional helper. Remove if not needed.
void reset_istream();

int main(int argc, char *argv[])
{
   cout<<"Please enter a, b, c seperated by spaces. Then press <enter>."<<endl;
   cout<<"a b c = ";
   double a, b, c;
   cin>>a>>b>>c;
   
   double det = b*b-4.0*a*c;
   double x1, x2;
   
   if(a == 0)
   {
      cout<<"Coefficient a is 0. This is not a quadratic equation!"<<endl;
   }
   else if (det < 0)
   {
      cout<<"This quadratic does not have real roots."<<endl;
   }
   else
   {
      x1 = (-b + sqrt(det) ) / (2.0*a);
      x2 = (-b - sqrt(det) ) / (2.0*a);
      
      cout<<"x1= "<<x1<<endl<<"x2= "<<x2<<endl;
   }

   reset_istream();
   wait_for_enter();
   return 0;
}

//---------------------------------------------------

void reset_istream()
{
   cin.clear();
   cin.ignore(numeric_limits<streamsize>::max(), '\n');
}

//---------------------------------------------------

void wait_for_enter()
{
  cout << "press <enter> to continue...";
  // Reset failstate, just in case.
  cin.clear();
  string line;
  getline( cin, line);
}