that is a driver code of library mathFromSinan.h

mathFromSinan.c

#include <stdio.h>
#include "mathFromSinan.h"

int factorialForInt(const int __input_Value )
{
	if( __input_Value == 0 || __input_Value == 1 )
		return 1;
	else
		return __input_Value * factorialForInt(__input_Value-1);
}

double factorialForDouble(const double __input_Value )
{
	if( __input_Value == 0 || __input_Value == 1 )
		return 1;
	else
		return __input_Value * factorialForDouble(__input_Value-1);
}


double power(double _base,int _power)
{
	double _temp = 1.0;
	int i;

	if(_power == 0)
		return 1;
	
	for(i=0;i<_power;++i)	
		_temp *= _base;

	return _temp;
}

double ePowerForInt(int __input_Value)
{
	int i;
	double temp = 0;

	for(i=0 ;i<__LIMIT_FOR_CALCULATION ;++i)
		temp += (power(__input_Value,i) / factorialForInt(i));

	return temp;
}

double ePowerForDouble(double __input_Value)
{
	int i;
	double temp = 0;

	for(i=0 ;i<__LIMIT_FOR_CALCULATION ;++i)
		temp += (power(__input_Value,i) / factorialForInt(i));

	return temp;
}

double sinus(double _radyan_Degree)
{
	int i;
	double temp = 0;

	for(i=0 ;i<__LIMIT_FOR_CALCULATION ;++i)
		temp += ( ( power(-1,i) * power(_radyan_Degree,2*i+1) ) / ( factorialForInt(2*i+1) ) );
	
	return temp;
}

double cosinus(double _radyan_Degree)
{
	int i;
	double temp = 0;

	for(i=0 ;i<__LIMIT_FOR_CALCULATION ;++i)
		temp += ( ( power(-1,i) * power(_radyan_Degree,2*i) ) / ( factorialForInt(2*i) ) );
	
	return temp;
}


double tangent(double _radyan_Degree)
{
	return sinus(_radyan_Degree) / cosinus(_radyan_Degree);
}


double cotangent(double _radyan_Degree)
{
	return cosinus(_radyan_Degree) / sinus(_radyan_Degree);
}

mathFromSinan.h

#ifndef __MATH__LIBRARY__FROM__SINAN__NAR__
#define __MATH__LIBRARY__FROM__SINAN__NAR__

#define __LIMIT_FOR_CALCULATION 17

#include<stdio.h>

int factorialForInt(const int __input_Value );
double factorialForDouble(const double __input_Value );

double power(double _base,int _power);

double ePowerForInt(int __input_Value);
double ePowerForDouble(double __input_Value);

double sinus(double _radyan_Degree);
double cosinus(double _radyan_Degree);
double tangent(double _radyan_Degree);
double cotangent(double _radyan_Degree);


#endif

testingTrigonametricFunctions.c

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

#include "mathFromSinan.h"

int main(void)
{
	printf("\n");
	printf("sinus from my own library\n");
	printf("%.10f\n",sinus(0.5));
	printf("from math.h library\n");
	printf("%.10f\n\n",sin(0.5));

	printf("cosinus from my own library\n");
	printf("%.10f\n",cosinus(0.5));
	printf("from math.h library\n");
	printf("%.10f\n\n",cos(0.5));

	printf("tangent from my own library\n");
	printf("%.10f\n",tangent(0.5));
	printf("from math.h library\n");
	printf("%.10f\n\n",tan(0.5));

	printf("cotangent from my own library\n");
	printf("%.10f\n",cotangent(0.5));
	printf("from math.h library\n");
	printf("%.10f\n",cos(0.5)/sin(0.5));
	printf("\n");

    return 0;
}

Using McLauren and Taylor series method to implement sinus,cosinus and so on...