Hello.How to develop a program that calculates the value of a function?

Question

[-1,1]
{sinx,-2<=x<=-1
{cose^x,-1<x<=0
y={tg lnx, 0<x<=1
{ctgx,1<x<=2

Answer 1

E.g.

double f(int x)
{
if (x <= -1) return (sin(x));
if (x <= 0) return (cos(x));
// more
}

// call in main

int main()
{
std::cout << f(1);
std::cout << f(2);
}

http://www.cplusplus.com/reference/cmath/