Dear all

This code is simulate some of math library funcs.

Good Luck!

//sin , cos , tan , cot , exp , pow , fabs & fibonachi simulation
//programming by : Erfan Nasoori
//Mail : ketn68@yahoo.com
//Date of send : 2009/2/7


#include <iostream>
#include <math> /*<cmath>*/
#include <conio>

class mymath{
		public:
			 double mysin(double);
			 double mycos(double);
                         double mytan(double);
                         double mycot(double);
			 double myexp(double);
			 double mypow(double,double);
                         double myfabs(double);
			 int    fibonachi1(int);
                         void   fibonachi2(long[],int);
	    };

/////////////////////////////////////////////////
double mymath :: mysin(double x)
{
 double f=1 , p=x , sum=0 , item=x;
 int i;
 for(i=1; fabs(item)>=1e-10 ; ++i)
 {
    sum += item;
    f *= (2*i+1)*(2*i);
    p *= (-x*x);
    item = p/f;
 }
 return sum;
}
/////////////////////////////////////////////////
double mymath :: mycos(double x)
{
 double f=1 , p=1 , sum=1 , item=1;
 int i;
 for(i=1; fabs(item)>=1e-10 ; ++i)
 {
    f *= (2*i-1)*(2*i);
    p *= (-x*x);
    item = p/f;
    sum += item;
 }
 return sum;
}
/////////////////////////////////////////////////
double mymath :: mytan(double x)
{
 if( mycos(x) != 0)
    return mysin(x)/mycos(x);
}
/////////////////////////////////////////////////
double mymath :: mycot(double x)
{
 if( mysin(x) != 0)
    return mycos(x)/mysin(x);
}
////////////////////////////////////////////////
double mymath :: myexp(double x)
{
 long double f=1 , sum=1 , p=1 , item;
 for(int i=1; i<1000 ; ++i)
 {
    f *= i;
    p *= x;
    item = p/f;
    sum += item;
 }
 return sum;
}
////////////////////////////////////////////////
double mymath :: myfabs(double x)
{
 return( x<0 ?  -x :  x );
}
////////////////////////////////////////////////
double mymath :: mypow(double x,double y)
{
 double z , p=1;
 //y<0 ? z=-y : z=y ;
 if(y<0)
    z = myfabs(y);
 else
    z = y;
 for(int i=0; i<z ; ++i)
 {
    p *= x;
 }
 if(y<0)
   return 1/p;
 else
   return p;
}
//////////////////////////////////////////////
int mymath :: fibonachi1(int x)
{
 int f1=1 , f2=1 , f3;
 f3 = f1;
 for(int i=3 ;i<=x;++i)
 {
    f3 = f1+f2;
    f1 = f2;
    f2 = f3;
 }
 return f3;
}
//////////////////////////////////////////////
void mymath :: fibonachi2(long fibo[],int x)
{
 long f1=1 , f2=1 , f3;
 for(int i=3 ;i<=x;++i)
 {
    fibo[i] = f1+f2;
    f1 = f2;
    f2 = fibo[i];
 }
}
/////////////////////////////////////////////////
int main()
{
 double si,co,tg,cotg,po,ex,fs,x,y,z;
 int i,j,num,fib1,fib2;
 long f3[50];
 char key;
 mymath m;
 do{
     clrscr();
     cout<<"which program do you want?\n"
    	 <<"1-sin\n"
  	 <<"2-cos\n"
         <<"3-tan\n"
  	 <<"4-cot\n"
  	 <<"5-exp\n"
  	 <<"6-pow\n"
         <<"7-fabs\n"
  	 <<"8-fibonachi(1)\n"
  	 <<"9-fibonachi(2)\n"
  	 <<"enter a number of one of them:\n";
     cin>>num;
     cout<<"~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;

                while(num<1 || num>9)
		{
		 cout<<"Please enter one of 1-2-3-4-5-6-7-8-9"
                     <<" inorder to starting program!\n";
                 cin>>num;
                 cout<<"~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
		 ++i;
		}

                if(num == 1)
 		{
 		 cout<<"Please enter x for sin function = ";   cin>>x;

 		 si = m.mysin(x);
 		 cout<<"sin("<<x<<") = "<<si<<"\n"
       	             <<"sin("<<x<<") of math.h headerfile = "<< sin(x)<<endl;
 		}

 		else if(num == 2)
 		{
 		 cout<<"Please enter x for cos function = ";   cin>>x;
 		 co = m.mycos(x);
 		 cout<<"cos("<<x<<") = "<<co<<"\n"
   		     <<"cos("<<x<<") of math.h headerfile = "<<cos(x)<<endl;
 		}

                else if(num == 3)
 		{
 		 cout<<"Please enter x for tan function = ";   cin>>x;
 		 tg = m.mytan(x);
 		 cout<<"tan("<<x<<") = "<<tg<<"\n"
   		     <<"tan("<<x<<") of math.h headerfile = "<<tan(x)<<endl;
 		}

                else if(num == 4)
 		{
 		 cout<<"Please enter x for cot function = ";   cin>>x;
 		 cotg = m.mycot(x);
 		 cout<<"cot("<<x<<") = "<<cotg<<"\n"
   		     <<"cot("<<x<<") of math.h headerfile = "<<(1/tan(x))<<endl;
 		}

  		else if(num == 5)
 		{
 		 cout<<"Please enter x for exponent function = ";   cin>>x;
 		 ex = m.myexp(x);
 		 cout<<"exp("<<x<<") = "<<ex<<"\n"
   		     <<"exp("<<x<<") of math.h headerfile = "<<exp(x)<<endl;
 		}

 		else if(num == 6)
 		{
 		 cout<<"Please enter x for power function = ";   cin>>x;
 		 cout<<"Please enter y for power function = ";   cin>>y;
 		 po = m.mypow(x,y);
 		 cout<<"pow("<<x<<","<<y<<") = "<<po<<"\n"
   		     <<"pow("<<x<<","<<y<<") of math.h headerfile = "
                     <<pow(x,y)<<endl;
 		}

                else if(num == 7)
 		{
 		 cout<<"Please enter a number = ";   cin>>x;
 		 fs = m.myfabs(x);
 		 cout<<"fabs("<<x<<") = "<<fs<<"\n"
   		     <<"fabs("<<x<<") of math.h headerfile = "
                     <<fabs(x)<<endl;
 		}

 		else if(num == 8)
                {
 		 cout<<"which number do you want to show ?"<<endl;
 		 cin>>x;
   		 while(x <= 0)
                 {
     		   cout<<"Try again : ";
     		   cin>>x;
                   ++i;
                 }
 		 fib1 = m.fibonachi1(x);
 		 cout<<x<<"th number of fibonachi seri = "<<fib1<<endl;
 		}

		else
                {
   		 cout<<"How many numbers of fibonachi "
                     <<"seri do you want to show?\n";
   		 cin>>x;
   		 while(x <= 0)
                 {
        	   cout<<"Try again : ";
        	   cin>>x;
        	   ++i;
                 }
   		 m.fibonachi2(f3,x);

   		 cout<<x<<" numbers of fibonachi : "<<endl;
   		 if(x == 1)
   		   cout<<"1"<<endl;
   		 else
                 {
   		   cout<<"1 1 ";
   		   for(i=3 ; i<=x ; ++i)
   		      cout<<f3[i]<<" ";
     		 }
   		 cout<<endl;
                }
 
		cout<<"~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
		cout<<"do you want to continue (y/n) ? "<<endl;
                cin.ignore();
		key = getch();

   }while(key=='y'|| key=='Y');
 return 0;
}

Thanks for making this posting.

In mytan and mycot, not all paths return a value. What do you expect the function's behavior to be then? I would return NaN. Also those functions unnecessarily recalculate mycos and mysin once.

Your lines

if(y<0)
    z = myfabs(y);
else
    z = y;

are equivalent to just saying z = myfabs(y); .

OK
thats right
z = myfabs(y);

but i don't undrestand , is there any problem in mytan ? logical or mathematics etc.
its return value haven't problem , we can declare a double cell and transfer mysin/mycos to it and finally return this cell.
OK?