#include<stdio.h>
#include<math.h>
#include<conio.h>

double fx(double x);

void main(void)
{
char flag='a';
double a=0, b=1, c=0,err=0;
float er;
printf("\n\nEnter the allowable error:  ");
scanf("%f",&er);
err=(double)er;

while(  ( fx(a) * fx(b) ) >0 )
	{
	a++; b++;
	if(fx(a)<0)	flag='a';
	else flag='b';
	}

while(flag=='a' || flag=='b')
	{
	c=fx( (a+b)/2 );

	if(fabs(a-b)<err)
		{
		if(fabs(a)<fabs(b))
			flag='A';
		else flag='B';

		continue;
		}

	if(c<0)
		{
		if(flag=='a')
			a=((a+b)/2);
		else if(flag=='b')
			b=((a+b)/2);

		continue;
		}

	else if(c>0)
		{
		if(flag=='a')
			b=((a+b)/2);
		else if(flag=='b')
			a=((a+b)/2);

		continue;
		}

	else if(c==0)
		{
		printf("\n\n%f is an EXACT root of the eqn. given",(a+b)/2);
		break;
		}
	}
if(flag=='A') printf("\nThe Approx. first root is: %f",a);
else 	    printf("\nThe Approx. first root is: %f",b);

while(!kbhit()) ;
}

double fx(double x)
{
double temp;
temp=3*sin(3*x)-2*cos(2*x)+7*atan(8*x/7.3);
return temp;
}