C++ Program to Compute the Sine and Cosine Series

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The program for sine and cosine is based on power series especially Taylor series. A power series is a form of representation of some functions that converge into a single value.

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In simple words, some functions are in the form of an infinite series (A power series is also a form of infinite series) can give a finite value.

This program computes that finite value for a sine and cosine series and prints the result. To understand the mathematical part of the program, you must learn – sequences and series, calculus, infinite series, power series (Taylor series, Maclaurin series).

If you are not familiar with the above concepts continue reading the following sections – problem definition, flowchart, program source code and verifies the output. This program is intended for intermediate level learners of C programming language.

Problem Definition

The formula for computing the sine and cosine series for a given degree, X is





First, you change the value of x to radian and then using the result compute the sine and cosine series. To understand the concept, let’s take an example.

Suppose x = 45 degree

We want to compute sine (45), then convert 45 degrees into radian measure.

radian = 45 * π/180

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= π/4

= 3.14/4

= 0.785398

Now, it is easy to compute the value of sin (π/4). Use the radian value in the series given above figure and get the following results.

sin (x) = 0.785398 – (0.785398)3/3! + (0.785398)5/5! …

sin (x) = 0.7072 (computed using calculator)

Note: The same principle applies to cosine series.

How do we process the input values ?

The process of computing sine and cosine series is described in 4 steps.

1. Convert the degree to radian value for sine and cosine series computation.
2. Compute the value of sin (x), where x is a value in radians.
3. Compute the value of cos (x), where x is a value in radians.
4. Print the result of the computation.

Flowchart – Sine and Cosine Series

Program Code – Sine and Cosine Series

/* Program to Compute Sine AND Cosine Series using following formula

Sin x = x - x^3/3! + x^5/5! -x^7/7! +...

Cosine x = x - x^2/2! + x^4/4! - x^6/6! + ... */

#include <iostream.h>
#include <stdlib.h>
#include <cmath>
#include <stdio.h>
#include <conio.h>


#define PI 3.14

// Function Declaration Section

float factorial(int exponent);
int menu();
void compute_sine();
void compute_cosine();

//Global Declaration Section

int deg; float rad,deno,numa,result;
int exponent;
int n,i,t;

// MAIN FUNCTION BEGINS HERE

int main()
{

    menu();

    system("PAUSE");

    return 0;

}

//Main ends here

void compute_sine()
{

    n = 11;

    result = 0.0;

//Compute the radian equivalent for the "deg" entered

    rad = deg * PI/180;

//Compute the series for Radian measure of Sine

for( i = 0;i< n;i++) {

    exponent = (2 * i) + 1;

    numa = pow(rad,exponent);

    deno = factorial(exponent);

    result = result + ((numa * pow(-1,i))/deno);

}

//Display the results

    cout << "Sin " << deg << "=" << "t"
    << setprecision(2) << result << endl;

}

//Function Factorial

float factorial(int exponent)
{

    int i;

    float fact = 1.0;

for(i = 1;i <= exponent;i++)
{

    fact = fact * i;

}

    return(fact);

}

//Function Menu Definition

int menu()
{

    int ch;

while(ch != 3)
{

    for(i=0;i < 35;i++)
    cout << "*" ;cout << endl;

    cout << "Enter the Degree:"; cin >> deg;

    for(i=0;i < 35;i++)
    cout << "_" ;cout << endl;

    cout << "1.SINE SERIES" << endl;
    cout << "2.COSINE SERIES" << endl;
    cout << "3.EXIT" << endl;

    for(i=0;i < 35;i++)
    cout << "_" ;cout << endl;

    cout << " Enter Your Choice:";
    cin << ch;

switch(ch)
{

    case 1: compute_sine();
    break;

    case 2: compute_cosine();
    break;

    case 3: exit(0);
    default:

    cout << "OOPs! Wrong Choice:" << endl;
    break;

     }
   }
}

// Compute_Cosine function definition

void compute_cosine()
{

    n = 11;
    result = 0.0;

//Compute the Radian equivalent for the "deg" entered

    rad = deg * PI/180;

//Compute the series for Radian measure of Sine

for( i = 0;i < n;i++)
{

    exponent = 2 * i;

    numa = pow(rad,exponent);

    deno = factorial(exponent);

    result = result + ((numa * pow(-1,i))/deno);

}

//Display the results

    cout << "Cosine " << deg << "t" << "=" << "\t" << setprecision(2) << result << endl;

}

Output

The output of the above program is given below. First you have to test the value of sine series and then verify output of cosine series.

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