I'm writing a simple program that solves a quadratic equation. I have to input a b c numbers in one line, but I can't do this.
My solution:
1
2
-4
But I need that input:
1 2 -4
This is my solution with 3 lines input instead one line input. Sorry for my bad english.
package com.sircascado;
import java.util.Scanner;
import java.lang.Math;
class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
double a = sc.nextDouble();
double b = sc.nextDouble();
double c = sc.nextDouble();
double d = (b * b) - (4 * a * c);
double x1 = (-b - Math.sqrt(d)) / (2 * a);
double x2 = (-b + Math.sqrt(d)) / (2 * a);
System.out.println(Math.ceil(x1 + x2) + " " + Math.ceil(x1 * x2));
}
}
Related
This question already has answers here:
Int division: Why is the result of 1/3 == 0?
(19 answers)
Closed 2 years ago.
This is the problem: Write a program that prompts for the lengths of the sides of a triangle and reports the three angles.
I have written the following code for it:
public static void main(String[] args) {
Scanner console = new Scanner(System.in);
System.out.print("Please input length of side A: ");
int sideA = console.nextInt();
System.out.print("Please input length of side B: ");
int sideB = console.nextInt();
System.out.print("Please input length of side C: ");
int sideC = console.nextInt();
System.out.println();
System.out.println("The angle between A and B is: " + calculateAngle(sideA, sideB, sideC));
System.out.println("The angle between B and C is: " + calculateAngle(sideB, sideC, sideA));
System.out.println("The angle between C and A is: " + calculateAngle(sideC, sideA, sideB));
}
public static double calculateAngle(int a, int b, int c) {
return Math.toDegrees(Math.acos((a * a + b * b - c * c) / (2 * a * b)));
}
Here is a sample output from my code above:
Please input length of side A: 55
Please input length of side B: 22
Please input length of side C: 76
The angle between A and B is: 90.0
The angle between B and C is: 90.0
The angle between C and A is: 90.0
No matter what values I input for the sides, the only angles I ever get are 90 or 180 degrees, never the actual correct angle that can be calculated from the cosine rule. What is wrong with my code?
Just cast the calculation in Math.acos to double :
return Math.toDegrees(Math.acos((double)(a * a + b * b - c * c) / (2 * a * b)));
As you could see in comments, when computing between multiple int types, the integer arithmetic is used and then casted to double.
Also it's worth noting, that int always round down, meaning:
int i = 0.9999999; // i = 0
According to documentation they are expecting a double value as their parameter for acos method JavaSE7 Math doc
so re-arrange your code like this
public static void main(String[] args) {
Scanner console = new Scanner(System.in);
System.out.print("Please input length of side A: ");
double sideA = console.nextDouble();
System.out.print("Please input length of side B: ");
double sideB = console.nextDouble();
System.out.print("Please input length of side C: ");
double sideC = console.nextDouble();
System.out.println();
System.out.println("The angle between A and B is: " + calculateAngle(sideA, sideB, sideC));
System.out.println("The angle between B and C is: " + calculateAngle(sideB, sideC, sideA));
System.out.println("The angle between C and A is: " + calculateAngle(sideC, sideA, sideB));
}
public static double calculateAngle(double a, double b, double c) {
return Math.toDegrees(Math.acos((a * a + b * b - c * c) / (2 * a * b)));
}
I am working on a function for the quadratic formula in java eclipse mars, and when I compile the code it outputs NaN when mathematically this answer is possible and i should get 2.0 please help
import java.util.Scanner;
public class Quadradic1 {
public static void main(String[] args) {
double a;
double b;
double c;
double x;
System.out.print("Input A B C: ");
Scanner input = new Scanner(System.in);
a = input.nextDouble();
b = input.nextDouble();
c = input.nextDouble();
x = (-b + Math.sqrt(b * b + 4 * a * c))/(2 * a);
System.out.println("Quadratic1 " + x);
}
}
Sorry the values I entered are a=1 b=2 and c=-8
For your inputs
b * b + 4 * a * c evaluates to -28. There is not such thing as the square root of a negative number
I have code that is supposed to solve a quadratic equation but yields NaN as a result.
I've looked around for 2 days now and I can't find a solution. Any and all advice will be more than appreciated!
package quadratic;
import java.util.Scanner;
public class Formlua {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter value of A ");
double a = input.nextDouble();
System.out.println("enter value of B ");
double b = input.nextDouble();
System.out.println("enter value of C ");
double c = input.nextDouble();
double four = 4;
double square = Math.sqrt(b* b - 4 * a * c );
double root1 = (-b + square) / (2*a);
double root2 = (-b - square) / (2*a);
System.out.println("The answer is " + root1 + "and" + root2);
System.out.println("Do you want to continue? y/n");
String user = input.toString();
if(user.equalsIgnoreCase("y"));
}
}
This code:
Math.sqrt(b* b - 4 * a * c );
can result in NaN ("not a number").
If the value of b* b - 4 * a * c is negative, there are solutions only in complex numbers (but not in double data type)
There should be a condition
if (b* b - 4 * a * c<0) {
System.out.println("There is no solution in real numbers");
return;
}
The most likely cause of the problem is Math.sqrt(b*b - 4 * a * c). or one of your input values is NaN (probably not the cause in this situation).
There are two special cases:
b *b < 4 * a * c
and a = 0
if b * b < 4 * a * c your answer is in the complex plane (specifically, not a real number).
if a = 0 then you actually just have a linear equation.
you could try the following code:
package quadratic;
import java.util.Scanner;
public class Formlua {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter value of A ");
double a = input.nextDouble();
System.out.println("enter value of B ");
double b = input.nextDouble();
System.out.println("enter value of C ");
double c = input.nextDouble();
if (a == 0){
// 0 = 0*x*x + b*x + c ==> x = -c/b
System.out.println("X = " + Double.toString(-c/b));
} else {
double inner = b * b - 4 * a * c;
if (inner < 0){
inner = -inner;
inner = Math.sqrt(inner);
System.out.println("X = " + Double.toString(-b) + " + " + Double.toString(inner) + "i")
System.out.println(" = " + Double.toString(-b) + " - " + Double.toString(inner) + "i");
} else {
inner = Math.sqrt(inner);
System.out.println("X = " + Double.toString(-b));
if (inner == 0){
} else {
System.out.println("X = " + Double.toString(-b + inner));
System.out.println("X = " + Double.toString(-b - inner));
}
}
}
}
This lets your user input any double values and recieve an answer.
Okay so I am a complete Java noob, and I'm trying to create a program for class that runs a quadratic equation using scanner inputs. So far what I've got is this:
import java.util.*;
public class QuadraticFormulaSCN {
public static void main(String[]args) {
System.out.println("insert value for a:");
Scanner scan1 = new Scanner(System.in);
double a = scan1.nextDouble();
System.out.println("insert value for b:");
Scanner scan2 = new Scanner(System.in);
double b = scan2.nextDouble();
System.out.println("insert value for C:");
Scanner scan3 = new Scanner(System.in);
double c = scan3.nextDouble();
double answer =((Math.sqrt(Math.pow(b,2)-(4*a*c))-b)/2);
double final2 =(-b + Math.sqrt(Math.pow(b,2)-(4*a*c)))/2;
System.out.println("The x values are:" + answer + final2);
}
}
But I get a weird output, specifically NaNaN... What do I do to fix this? What am I doing wrong?
I'm a little late to answer, but I corrected your problems (described in the other answers), fixed one of your calculations, and cleaned up your code.
import java.util.*;
public class Test {
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
System.out.println("Insert value for a: ");
double a = Double.parseDouble(s.nextLine());
System.out.println("Insert value for b: ");
double b = Double.parseDouble(s.nextLine());
System.out.println("Insert value for c: ");
double c = Double.parseDouble(s.nextLine());
s.close();
double answer1 = (-b + Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
double answer2 = (-b - Math.sqrt(Math.pow(b, 2) - (4 * a * c))) / (2 * a);
if (Double.isNaN(answer1) || Double.isNaN(answer2))
{
System.out.println("Answer contains imaginary numbers");
} else System.out.println("The values are: " + answer1 + ", " + answer2);
}
}
NaN is something you get when the calculation is invalid. Such as dividing by 0 or taking the squareroot of -1.
When I test your code with a = 1, b = 0 and c = -4 the answers is 2.02.0
The formatting is not right and the calculation of final2 is not negated.
Otherwise the code is right.
To improve you could check whether the discriminant is negative.
double d = b*b -4 * a * c;
if (d < 0){
System.out.println("Discriminant < 0, no real solutions" );
return;
}
double x1 = (-b -sqrt(d))/(2*a);
double x2 = (-b +sqrt(d))/(2*a);
System.out.format("The roots of your quadratic formula are %5.3f and %5.3f\n",x1,x2);
Or, if you prefer support for solutions from the complex domain:
if (d < 0) {
System.out.println("Discriminant < 0, only imaginary solutions");
double r = -b / (2 * a);
double i1 = -sqrt(-d) / (2 / a);
double i2 = sqrt(-d) / (2 / a);
System.out.format("The roots of your quadratic formula are (%5.3f + %5.3fi) and (%5.3f + %5.3fi)\n",r, i1, r, i2);
return;
}
You are getting NaN because you are attempting to take the square root of a negative number. In math that's not allowed unless you are allowing complex numbers, e.g. 1 +/- 2i.
This can happen in quadratic formulas when the discriminant (the thing in the square root) is negative, e.g. x^2 + 6*x + 100: b^2 - 4ac = 36 - 400 = -364. Taking the square root of a negative number in Java leads to NaN. (not a number)
To test for NaN, use Double.isNaN and handle the NaN appropriately.
In addition, your calculations are incorrect even if NaN isn't being encountered:
$ java QuadraticFormulaSCN
insert value for a:
1
insert value for b:
5
insert value for C:
6
The x values are:-2.0-2.0
This should have outputted 2.0 and 3.0
You should only do the calculation when
discriminant is equal or greater than zero
if(((Math.pow(b,2)-(4*a*c))>= 0){ /* Calculation here */ }
else {/*error message or complex number calculus*/};
One thing I always try to do is put all my math in appropriate parenthesis to avoid an, all too easy, Order of Operations mistake. The NaN is saying "Not a number." You would also get that message if the user input numbers that could not produce a result, such as a trying to get the square root of a negative number. Also, just as a note, you can save sometime by only using on Scanner for a,b, and c.
public class QuadraticFormula{
public static void main(String[] args){
java.util.Scanner input = new java.util.Scanner(System.in);
double a = input.nextDouble();
double b = input.nextDouble();
double c = input.nextDouble();
double quadPos = (-b + Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
double quadNeg = (-b - Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
System.out.println("-b - = " + quadNeg + "\n-b + = " + quadPos);
}
}
This is the code that I have thus far. The goal of the project is to have the user enter any integers for a, b, c for the ax^2+bx+c equation. For some reason I am not getting the correct roots for any numbers that are input into the program. Can anyone point out my wrong doings?
import java.util.*;
public class Quad_Form {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
double a = 0;
double b = 0;
double c = 0;
double discrim = 0;
double d = 0;
System.out.println("Enter value for 'a'");
String str_a = sc.nextLine();
a = Integer.parseInt(str_a);
System.out.println("Enter value for 'b'");
String str_b = sc.nextLine();
b = Integer.parseInt(str_b);
System.out.println("Enter value for 'c'");
String str_c = sc.nextLine();
c = Integer.parseInt(str_c);
double x1 = 0, x2 = 0;
discrim = (Math.pow(b, 2.0)) - (4 * a * c);
d = Math.sqrt(discrim);
if(discrim == 0){
x1 = (-b + d) / (2* a);
String root_1 = Double.toString(x1);
System.out.println("There is one root at: " + root_1);
}
else {
if (discrim > 0)
x1 = (-b + d) / (2 * a);
x2 = (-b - d) / (2 * a);
String root_1 = Double.toString(x1);
String root_2 = Double.toString(x2);
System.out.println("There are two real roots at:" + root_1 + "and" + root_2);
}
if (discrim < 0){
x1 = (-b + d) / (2 * a);
x2 = (-b - d) / (2 * a);
String root_1 = Double.toString(x1);
String root_2 = Double.toString(x2);
System.out.println("There are two imaginary roots at:" + root_1 + "and" + root_2);
}
}
}
#Smit is right about one of the issues, but there's a second one as well.
Math.sqrt(discrim) won't work when discrim is negative. You should be taking Math.sqrt(Math.abs(discrim)) instead.
a, b, c, d are double and you are parsing them as Integer. So this could be one of problem.
Use
Double.parseDouble();
Another problem is you can not make square root of negative numbers. This will result in NaN. For that use following, but you should handle that properly to get exact result.
Math.sqrt(Math.abs());
Moreover you should use following formula for getting roots
Taken from Wikipedia Quadratic equation
Class Double
Class Math