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#pragma once
#include <cmath>
namespace md5::math {
constexpr double PI = 3.141592653589793238462643L;
consteval double pow(double x, int n) {
double res = 1;
for (int i = 0; i < n; ++i) {
res *= x;
}
return res;
}
consteval double factorial(int n) {
double res = 1;
for (int i = 2 ; i <= n ; ++i) {
res *= i;
}
return res;
}
/// Calculate sin(x) value with Maclaurin series.
consteval double sin_core(double x) {
double res = x;
for (int i = 1; i < 80; ++i) {
const int n = i * 2 + 1;
const int sign = (i & 1) ? -1 : 1;
res += sign * pow(x, n) / factorial(n);
}
return res;
}
/// Calculate the sin(x) value in radians.
consteval double sin(double x) {
x = std::fmod(x, 2 * PI); // -2PI < x < 2PI
if (std::abs(x) > PI) {
x -= ((x > 0) ? 2 : -2) * PI; // -PI < x < PI
}
if (std::abs(x) > PI / 2) {
x = ((x > 0) ? 1 : -1) * PI - x; // -PI / 2 < x < PI / 2
}
return sin_core(x);
}
} // namespace md5::math