Thread: Sine (Sin) Algorithm Help

Okay, this is my attempt to get the required results that are in the first post:

Code:

double sin(float angle)
{
        double guess;
        for (guess = angle; !(fabs(guess * guess - angle) < EPSILON); guess = ((x * guess * guess * -1) / ((guess * 2) +1)!)
		{		}

        return guess;
}

Well, it isn't compiling, so I'll take it as a no..lol

Thanks

But I have a different question now, (because I'm pretty sure I'm still doing something wrong.) I am compiling this program on a windows machine and I am supposed to use a static library which I thought was the .h extension at the end, but I had to change my program to a .c to make it go anywhere. Any ideas?

Here is my code.

Code:

#include <cstdlib>
#include <math.h>
#define EPSILON 0.000001




void sphere(float radius, float &surface, float &volume)
{
     #define PI 3.14159265358979323846264338327950288419716939937510582097494459

     float radSq = radius * radius;

     surface = 4 * PI * radSq;
     volume = (4 * PI * radius * radSq)/3;
}

float volCylinder(float radius, float height)
{
      float volume = (PI * radius * radius * height);
      return volume;
}

float sumFloats(float x[], int numFloats)
{
      float sum = 0.0;

      for(int i = 0 ; i < numFloats ; i++)
      {
              sum += x[i];
      }

      return sum;
}

double sine(float angle)
{
		int d = 1;
        double guess = 0;
        int i = 1;
        float x2p1 = angle;
        for(guess = angle; guess * guess - angle < EPSILON || guess * guess - angle < -EPSILON; guess = (x2p1 / (d *((i * 2) +1)*(i *2))))
		{
			x2p1 = x2p1 * angle * angle * -1;
			i = i +1;
		}

        return guess;
}

And here is my supposed main program:

Code:

#include <fstream>    // fstream.h contains file sequential IO methods.
#include <stdlib.h> // stdlib.h contains the exit method.
#include <stdio.h>
#include <string.h>
#include "mathlib.c"

using namespace std;

int main( )
{

	char fileOutName[25];
	char response;
	int n = 0;
	int choice = 0;
	int again = 1;
	float angle = 0.0;
	float sum = 0.0;
	float radius = 0.0;
	float surface = 0.0;
	float volume = 0.0;
	float height = 0.0;
	int filecount = 0;  //The number of lines in the file.

	FILE *outFile;			   // Logical output file name in program.

	//Gets the file out name and then checks to see if it already exists
	//If so then it asks for you to choose whether or not to override.
	printf("What is the name of the output file (max 25 characters)?");
	scanf("%s", &fileOutName);
	if((outFile = fopen(fileOutName, "r" )) != NULL )
		{
			printf("\nA file by the name %s exists.\n", fileOutName);
			printf("Do you wish to overwrite (Y or N): ");
			//Skip <cr> in buffer with "%*c", i.e., one character
			scanf("%*c %c", &response);

			if( (response == 'n') || (response == 'N') )
			{ // should close file first
				printf("\nProgram aborted to prevent overwirte!");
				exit(1);
			}
		}
		outFile = fopen( fileOutName, "wt" );
		if( outFile == NULL )
		{
			printf("Could not create the output file! Program terminating.");
			exit(1);
		}

	while (again == 1)
	{
		printf("What would you like to do? 1 for Sphere, 2 for Cylinder, 3 for float addition, 4 for sin.\n");
		scanf("%d", choice);
		if (choice == 1)
		{
			printf("What is the radius of the sphere?\n");
			scanf("%f", radius);
			sphere(radius, surface, volume);
			printf("The sphere with a radius of %f has a surface of %f and a volume of %f.\n", radius, surface, volume);
			fprintf(outFile, "The sphere with a radius of %f has a surface of %f and a volume of %f. \n", radius, surface, volume);
			printf("Go again? (1 for yes, 2 for no)\n");
			scanf("%d", again);
		}
		else if (choice == 2)
		{
			printf("What is the radius of the cylinder?\n");
			scanf("%f", radius);
			printf("What is the height of the cylinder?\n");
			scanf("%f", height);
			volume = volCylinder(radius, height);
			printf("The cylinder with a radius of %f and a height of %f has a volume of %f.\n", radius, height, volume);
			fprintf(outFile, "The cylinder with a radius of %f and a height of %f has a volume of %f.\n", radius, height, volume);
			printf("Go again? (1 for yes, 2 for no)\n");
			scanf("%d", again);
		}
		else if (choice == 3)
		{
			printf("How many floats are being processed? \n");
			scanf("%d", n);
			float x[n];
			for (i = 0; i < n; i++)
			{
				printf("What is the float?\n");
				scanf("%f", x[i]);
			}
			for (j = 0; j < n - 1; j++)
			{
				for (k = j + 1; k < n; K++)
				{
					if (x[j] > x[k])
					{
						int temp = x[j];
						x[j] = x[k];
						x[k] = temp;
					}
				}
			}
			sum = sumFloats(x[], n);
			printf("The sum of the floats is %f. \n", sum);
			fprintf(outFile, "The sum of the floats is %f. \n", sum);
			printf("Go again? (1 for yes, 2 for no)\n");
			scanf("%d", again);
		}
		else if (choice == 4)
		{
			printf("What is the angle? \n");
			scanf("%f", angle);
			double answer = sin(angle);
			printf("The sin of angle %f is %f. \n", angle, answer);
			fprintf(outFile, "The sin of angle %f is %f. \n", angle, answer);
			printf("Go again? (1 for yes, 2 for no)\n");
			scanf("%d", again);
		}
		else
		{
			printf("Quitting.");
			again = 2;
		}
	}

	fclose(outFile);

	return 0;
}

Awesome, thanks.

Is there any compilers that you guys would recommend to use? I'm using visual studio 8 command prompt and I don't think it is very good, but I've been able to use it before. Anyways, I was just wondering. And if you know how to do a compile of a header file on it then I'd appreciate it.

Originally Posted by laserlight

You should have learnt this in elementary mathematics, but perhaps you are not familiar with the term: Summation Notation


That is a recurrence relation, not a sum expressed in summation notation.

I didnt learn how to use the sigma until a few months ago, honestly never saw it through grade school high school, 4 years of college (electronics even) and 10 years in industry. I had to ask a friend of mine what it meant because I was explaining a training concept for neural networks to him and he wanted the formula in that format, lol.