Помогите

#include <iostream>
#include <cmath>

/// Function which computes first task.
inline double taskA(double x, double y, double z)
{
	return 16.0 * y * y + exp(y * z) + pow(z + 1.51, 1.0/3.0) + log(y * z);
}
/// Function which computes single value of second task.
inline double taskB(double x)
{
	if(x < 3.0)
		return cos(pow(x, 0.3));
	if(x > 4.0)
		return 1.0 / tan(x * x);
	return sqrt(x * x * x + log10(x));
}
/// Function which represents operators in sigma function of third task.
inline double taskCInSigmaFunction(double x, double h)
{
	double h2p1 = 2 * h + 1; // temporary value
	return pow(x - 1, h2p1) / (h2p1 * pow(x + 1, h2p1));
}
/// @brief Function which computes third task.
/// @param x The x parameter of function.
/// @param a The lower bound of interval.
/// @param b The upper bound of interval.
/// @param step The step value for h parameter.
/// @param d An error value.
inline double taskC(double x, double a, double b, double step, double d)
{
	double sum = 0.0f;
	for(double h = a; h <= b; h += step)
	{
		double value =  taskCInSigmaFunction(x, h);
		if(value < d)
			break;
		sum += value;
	}
	return 2 * sum;
}

int main(void)
{
	// print first task result
	std::cout<<"First task result: "<<taskA(1.839, 3.821, 0.349)<<std::endl;
	// print second task result
	std::cout<<"Second task results: ";
	for(double x = 1.0; x <= 2.0; x += 0.2)
		std::cout<<taskB(x)<<", ";
	std::cout<<std::endl;
	// print third task result
	std::cout<<"Enter value for X parameter of function from third task: ";
	double x;
	std::cin>>x;
	std::cout<<"Third task result: "<<taskC(x, 1.0, 1.2, 0.02, 0.000001)<<std::endl;
}