Sine rule problems.

[skace]

Hello, I am trying to make a program that can use the sine rule to calculate the missing side of a triangle. However, the program keeps returning incorrect answers. Thanks for any help!

#include <iostream>
#include <stdio.h>
#include <math.h>
#include <string>
#include <cmath>

using namespace std;

double a_side;
double a_angle;
double b_angle;

double sin_rule_side_function (double a_side, double a_angle, double b_angle)
{
       return (sin(b_angle) * a_side / sin(a_angle));
}

int main (){
                cout << "Insert your A side." << endl;
                cin >> a_side;
                cout << "Insert your A angle." << endl;
                cin >> a_angle;
                cout << "Insert your B angle." << endl;
                cin >> b_angle;
                double b_angle_answer;
                {
                double b_angle_answer = sin_rule_side_function(a_side, a_angle, b_angle);
                cout << "Your answer is " << b_angle_answer << endl;
                }
system("pause");
}

[Veltas]

Before looking at the program a stupid question: are you using degrees or radians?

[skace]

Not so stupid question, the answer is default :S I have no idea how to change it.

Thanks for the quick response!

[Veltas]

Is there any particular reason why starting on line 26 there is another curly parantheses block?

[Veltas]

The angles in C use radians because it's faster to calculate it that way. If you want to use degrees you'll have to convert it.

EDIT: Faster, or easier as the case my be.

[skace]

How do I do that?

[Veltas]

http://en.wikipedia.org/wiki/Radians

Well, a full-circle angle in degrees is 360 degrees, right?

A full-circle angle in radians is 2 pi radians.

So to convert from radians to degrees multiply by (360 / 2 pi).

To convert from degrees to radians multiply by (2 pi / 360).

[Veltas]

45 degrees is 1/4 pi, 30 degrees is 1/6 pi.

[skace]

Sorry, I am really having trouble converting the units correctly. I've been trying to figure it out for a while and I still can't seem to do it. Any ideas?

[Chervil]

#include <iostream>
#include <cmath>

    using namespace std;
    
const double pi = 3.1415926535897932385;    

int main()
{
    double degrees = 30;
    double radians = degrees * pi / 180.0; // Convert degrees to radians
    cout << "the sine of " << degrees 
         << " degrees is " << sin(radians) << endl;
      
    double num = sqrt(3)/2.0;
    radians = asin(num);
    degrees = radians * 180.0 / pi;        // Convert radians to degrees
    cout << "The angle whose sine is " << num 
         << " is " << degrees << " degrees" << endl;
    
    return 0;
}

Output:

the sine of 30 degrees is 0.5
The angle whose sine is 0.866025 is 60 degrees

[skace]

Thank you! :)