Quadratic Equation Program

sl02ggp · #1 02-Nov-2009, 15:42

I have my program below (it runs and compiles as is) , but having difficulty implement these conditions and outputs:

conditions:
1. rejecting certain coefficients if the discriminat (B^(2) -4AC) <0.
2. also having no division by zero in my program (do i use setPrecision)?

outputs:
having at least 15 spaces or so for each of the root ouput and outputting the roots in the following format:
-right justified, four decimal places accuracy, fixed point format
-right justified, two decimal places accuracy, floating point (scientific) format
- left justified, four decimal places accuracy, fixed point format
- left justified, two decimal places accuracy, floating point (scientific) format

CPP / C++ / C Code:


// Quadratic Equation.cpp : main project file.
#include<stdio.h>
#include<math.h>

int main()
{
      int A, B, C;
      double disc, deno, x1, x2;
      printf("\n\n\t ENTER THE VALUES OF A,B,C...");
      scanf("%d,%d,%d", &A, &B, &C);
      disc = (B * B) - (4 * A * C);
      deno = 2 * A;
      if(disc > 0)
      {
             printf("\n\t THE ROOTS ARE REAL ROOTS");
             x1 = (-B/deno) + (sqrt(disc) / deno);
             x2 = (-B/deno) - (sqrt(disc) / deno);
             printf("\n\n\t THE ROOTS ARE...: %f and %f\n", x1, x2);
      }
      else if(disc == 0)
      {
             printf("\n\t THE ROOTS ARE REPEATED ROOTS");
             x1 = -B/deno;
             printf("\n\n\t THE ROOT IS...: %f\n", x1);
      }
      else
             printf("\n\t THE ROOTS ARE IMAGINARY ROOTS\n");
}

fakepoo · #2 02-Nov-2009, 16:07

Quote:

Originally Posted by sl02ggp

...
-right justified, four decimal places accuracy, fixed point format
-right justified, two decimal places accuracy, floating point (scientific) format
- left justified, four decimal places accuracy, fixed point format
- left justified, two decimal places accuracy, floating point (scientific) format
...

printf() can do all of these things.

sl02ggp · #3 02-Nov-2009, 16:09

lol...yes i know..... but can you be more specific please :]

also how do i implement the conditions too! actually want to use cout and cin instead..how would i implement this into my code.

Thank You!

fakepoo · #4 02-Nov-2009, 16:31

Look at this example for using fixed point or scientific notation. Look at this example for justifying right or left.

As for implementing the conditions, what is the question/problem?

sl02ggp · #5 02-Nov-2009, 16:37

here is the full problem that im trying to do:
trying to make a a program that finds the roots of a quadratic equation. (form: Ax^(2) + Bx + C = 0). Going to prompt the user to enter the coefficients A, B, and C. Also the program can only handle real roots, thus like i said before reject the coefficients if the discriminant (B^(2)-4AC)<0. Also, trying to make the program treat the quadratic equation as a special case, a linear equation, when A is zero. So...like i said before...no division by zero will occur.

sl02ggp · #6 02-Nov-2009, 16:39

still kind of confused after reading over the two links you gave me

changed my code:

CPP / C++ / C Code:


// Quadratic Equation.cpp : main project file.
#include <cmath>  // defines the sqrt() function
#include <iostream>
using namespace std;

int main()
{ // implements the quadratic formula
  float a, b, c;
 
  cout << "Enter the coefficients of a quadratic equation:" << endl;
  cout << "a: ";
  cin >> a;
  cout << "b: ";
  cin >> b;
  cout << "c: ";
  cin >> c;

  cout << "The roots of " << a << "*x*x + " << b
       << "*x + " << c << " = 0" << endl;
  
  float d = b*b - 4*a*c;  // discriminant
  float sqrtd = sqrt(d);
  float x1 = (-b + sqrtd)/(2*a);
  float x2 = (-b - sqrtd)/(2*a);
  
  cout << "are:" << endl;
  cout << "x1 = " << x1 << endl;
  cout << "x2 = " << x2 << endl;

}

fakepoo · #7 02-Nov-2009, 17:39

CPP / C++ / C Code:

float number = 1.23;

// output in fixed-point notation
cout << fixed << number; 

// output in scientific notation
cout << scientific << number;

sl02ggp · #8 02-Nov-2009, 21:24

here is my updated code with the justification, scientific/fixed, and spaces

still don't know how to set my code: where it rejects coefficients if the discriminant (B^(2)-4AC) <0. Also having no division of zero in my program (do i use setPrecision) and how ?

CPP / C++ / C Code:


// Quadratic Equation.cpp : main project file.
#include <cmath>  // defines the sqrt() function
#include <iostream>
#include <iomanip>
using namespace std;

int main()
{ // implements the quadratic formula
  float a, b, c;
 
  cout << "Enter the coefficients of a quadratic equation:" << endl;
  cout << "a: ";
  cin >> a;
  cout << "b: ";
  cin >> b;
  cout << "c: ";
  cin >> c;

  cout << "The roots of " << a << "*x*x + " << b
	   << "*x + " << c << " = 0" << " are:" <<endl;
  
  float d = b*b - 4*a*c;  // discriminant
  float sqrtd = sqrt(d);
  float x1 = (-b + sqrtd)/(2*a);
  float x2 = (-b - sqrtd)/(2*a);
   
  cout.precision(4);
  cout << "x1 = " << endl;
  cout.width(12); cout << right << fixed << x1 << endl;
	
  cout.precision(4);
  cout << "x2 = " << endl;
  cout.width(12); cout << right << fixed << x2 << endl;

  cout << setw (15)<< " "<<endl;

  cout.precision(2);
  cout << "x1 = " << endl;
  cout.width(12); cout << right << scientific << x1 << endl;
	
  cout.precision(2);
  cout << "x2 = " << endl;
  cout.width(12); cout << right << scientific << x2 << endl;

  cout << setw (15)<< " "<<endl;

  cout.precision(4);
  cout << "x1 = " << endl;
  cout.width(12); cout << left << fixed << x1 << endl;
	
  cout.precision(4);
  cout << "x2 = " << endl;
  cout.width(12); cout << left << fixed << x2 << endl;

  cout << setw (15)<< " "<<endl;
  
  cout.precision(2);
  cout << "x1 = " << endl;
  cout.width(12); cout << left << scientific << x1 << endl;
	
  cout.precision(2);
  cout << "x2 = " << endl;
  cout.width(12); cout << left << scientific << x2 << endl;

}

fakepoo · #9 03-Nov-2009, 08:43

Since you know what you are going to divide by, simply check that it is not zero after you have collected the user input. For instance:

CPP / C++ / C Code:

cout << "Enter the coefficients of a quadratic equation:" << endl;
cout << "a: ";
cin >> a;
cout << "b: ";
cin >> b;
cout << "c: ";
cin >> c;

// Make sure we are not trying to divide by zero
if(a == 0.0)
{
  // Show error message and exit....or handle it however you wish
}

float d = b*b - 4*a*c;  // discriminant

// Makes sure the discriminant is not less than zero
if(d < 0.0)
{
  // Show error message and exit....or handle it however you wish
}

...

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