Here is the program to find the Cosine of the given angle for the user defined accuracy. This is a fast, reliable and robust program, which uses no sophisticated functions but a simple while loop and other math functions.

Logic: The program follows the mathematical cosine series, where cosine of the entered radian angle ? is,

The program asks the user to enter the Angle x° . Also it asks for the number of iterations ‘n’ that the cosine loop should iterate. As the iteration increases, the accuracy boosts up. After the desired loop, the resultant gets printed out. Similar algorithm can be set to find the Sine value of the given number.

#include<stdio.h>

#include<math.h>

void main()

{

float pow = 2.0, nr, dr = 1.0, x1, sum;

int i = 1,n,s = -1,x;

clrscr();

printf(“\n\n\t ENTER THE ANGLE…: “);

scanf(“%d”, &x);

x1 = 3.142 * (x / 180.0);

sum = 1.0;

nr = x1*x1;

printf(“\n\t ENTER THE NUMBER OF TERMS…: “);

scanf(“%d”,&n);

while(i<=n)

{

dr = dr * pow * (pow – 1.0);

sum = sum + (nr / (dr * s));

s = s * (-1);

pow = pow + 2.0;

nr = nr * x1 * x1;

i++;

}

printf(“\n\t THE SUM OF THE COS SERIES IS..: %0.3f”, sum);

getch();

}

Download exe and source code here.