calculating sin, cos, and tangent function

I am trying to calculate sin, cos, and tan. The program works but it gives it to me in radians. I needed the conversion to degrees which is sin(x) * PI / 180. when i do this it gives me the wrong answer, can someone help me out. this is my code:

#include <iostream>
using namespace std;
#include <iomanip>
#include <cmath>

const PI = 3.14159265359;


int main()

Code:

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{
  // constant variable can be used to specify array size
  const int arraySize = 45;
  int s[ arraySize ]; // array s has 45 elements
 
  cout << fixed << setprecision(6);

  for ( int i = 1; i <= arraySize; i++ ) // set the values
      s[i] = i++;

  cout <<"Angle\n" << "(Degrees)" << setw( 9 ) <<"Sine"<< setw(15)
            <<"Cosine"<< setw(14) <<"Tangent"<<endl;

  // output contents of array s in tabular format
  for ( int j = 1; j <= arraySize; j++ ) 
                cout << setw( 2 ) << j << setw( 20 ) << sin(j) << setw(13)
                    << cos(j * PI * 180) << setw(13) << tan(j) << endl;

  return 0;
} // end main

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cos(j * PI * 180) is not the same thing as: cos( j ) * ( 180 / pi )

Give PI a type; convert to radians for each of sin, cos, and tan -- like this, for example:

Code:

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sin(j * PI / 180)

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A guess is that you will also have to specify the type of 180
as in 180.0

i tried it but it calculates if it were sin(1) * PI / 180 -calculates as this wrong
instead of sin ( 1 * PI /180) - what i want it to do right

i tried putting

Code:

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const degree = PI / 180.00;
for ( int j = 1; j <= arraySize; j++ ) 
                cout << setw( 2 ) << j << setw( 20 ) << sin(j * degree) << setw(13)
                    << cos(j) << setw(13) << tan(j) << endl;

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You're not specifying a type for your constants, eg:

Code:

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const double PI = 3.14159;

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I think it defaults to int the way you have it

complete code, taking sin (1) as example:
sin(1) in radians = .841470
sin(1) in degrees = .017452

code calculates:
correct sin(1) in radians
wrong sin(1) in degrees -- calculates as if sin(1) * PI / 180. Correct conversion is supposed to be sin(1 * PI / 180.0 )

Code:

---

#include <iostream>
using namespace std;
#include <iomanip>
#include <cmath>

const PI = 3.14159265359;
const degree = PI / 180.0;

int main()
{
  // constant variable can be used to specify array size
  const int arraySize = 45;
  int s[ arraySize ]; // array s has 45 elements
 
  cout << setprecision(6);

  for ( int i = 1; i <= arraySize; i++ ) // set the values
      s[i] = i++;

  cout <<"Angle\n" << "(Degrees)" << setw( 9 ) <<"Sine"<< setw(15)
            <<"Cosine"<< setw(14) <<"Tangent"<<endl;

  // output contents of array s in tabular format
  for ( int j = 1; j <= arraySize; j++ ) 
                cout << setw( 2 ) << j << setw( 20 ) << sin(j) << setw(13)
                    << cos(j) << setw(13) << tan(j) << endl;

  return 0;
} // end main

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Arrays go from 0 to N-1, not 1 to N.

Stuff to look at:

Code:

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#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

const double PI = 3.14159265359;

int main()
{
  const int arraySize = 45;
 
  cout << fixed << setprecision(6);
  cout <<"Angle\n" << "(Degrees)" << setw( 9 ) <<"Sine"<< setw(15)
            <<"Cosine"<< setw(14) <<"Tangent"<<endl;

  for ( int j = 1; j <= arraySize; j++ ) 
                cout << setw(2)  << j
            << setw(20) << sin(j * PI / 180)
            << setw(13) << cos(j * PI / 180)
            << setw(13) << tan(j * PI / 180) << endl;

  return 0;
}

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thanks, why did i have to add const double pI so i can know for future reference

As mentioned previously...

Quote:

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Originally Posted by Dave_Sinkula

Give PI a type

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Quote:

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Originally Posted by JaWiB

You're not specifying a type for your constants, eg:

Code:

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const double PI = 3.14159;

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I think it defaults to int the way you have it

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...you need to specify a type.

Quote:

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thanks, why did i have to add const double pI so i can know for future reference

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The first thing you should have learned in C++ was how to declare a variable. I suggest you revisit those lessons. For every variable you declare, you have to specify a type, and 'const' is not a type.

Or just make a conversion function to hide some of the nastiness of repeatedly doing the same thing

Code:

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const double degToRad ( double deg ) {
  const double PI = 3.1415926;
  return deg * PI / 180.0;
}

int main ( ) {
  for ( int j = 0; j <= 45; j++ )
  cout << setw(2)  << j
            << setw(20) << sin(degToRad(j))
            << setw(13) << cos(degToRad(j))
            << setw(13) << tan(degToRad(j)) << endl;

}

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I did it like this:

Code:

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int number1;
cout << "enter number for tangens calculation" << endl;
cin >> number1;
int calc = number1 * (PI-variable / 180);
antwoord = tan(calc);

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Borland had included its value in the math.h library as M_PI 3.14159265358979323846.