Fake math.h substitute for embedded systems to calculate sin/cos values

fake_math.c

/**
 * A super simple sin/cos substitute based on taylor sequences
 * to avoid importing the math.h
 *
 * sin x = x - x^3/3! + x^5/5! -x^7/7! ...
 * cos x = 1 -x^2/2!+x^4/4!-x^6/6! ...
 */
// #include "math.h"
// #include <zephyr/kernel.h>

#include <stdio.h>

#define PI (3.14159265359f)
#define TERMS 7

float simple_sin(float rad)
{
    float sign = 1.0;
    if (rad < 0)
    {
        sign = -1.0;
        rad = -rad;
    }
    float res = 0;
    float term = rad;
    int k = 1;
    while (k < TERMS * 2)
    {
        res += term;
        k += 2;
        term *= -rad * rad / k / (k - 1);
    }

    return sign * res;
}

float simple_cos(float rad)
{
    if (rad < 0)
    {
        rad = -rad;
    }
    float res = 0;
    float term = 1;
    int k = 0;
    while (k < TERMS * 2)
    {
        res += term;
        k += 2;
        term *= -rad * rad / k / (k - 1);
    }
    return res;
}

// conver clockwise degrees into counter-clockwise radians
float deg_to_cc_rad(int deg)
{
    deg %= 360; // make it less than 360
    return -(deg * PI) / 180.0f;
}

// clockwise (accepts negatives too)
float sin_from_deg(int deg)
{
    return simple_sin(deg_to_cc_rad(deg));
}
float cos_from_deg(int deg)
{
    return simple_cos(deg_to_cc_rad(deg % 360));
}

int main()
{
    printf("Sin 0 %f\n", sin_from_deg(0));
    printf("Sin 30 %f\n", sin_from_deg(30));
    printf("Sin 45 %f\n", sin_from_deg(45));
    printf("Sin 60 %f\n", sin_from_deg(60));
    printf("Sin 90 %f\n", sin_from_deg(90));
    printf("Sin 110 %f\n", sin_from_deg(110));
    printf("Sin 150 %f\n", sin_from_deg(150));
    printf("Sin 180 %f\n", sin_from_deg(180));
    printf("------------\n");
    printf("Sin 0 %f\n", sin_from_deg(0));
    printf("Sin -30 %f\n", sin_from_deg(-30));
    printf("Sin -45 %f\n", sin_from_deg(-45));
    printf("Sin -60 %f\n", sin_from_deg(-60));
    printf("Sin -90 %f\n", sin_from_deg(-90));
    printf("Sin -110 %f\n", sin_from_deg(-110));
    printf("Sin -150 %f\n", sin_from_deg(-150));
    printf("Sin -180 %f\n", sin_from_deg(-180));
    printf("===============\n");
    printf("Cos 0 %f\n", cos_from_deg(0));
    printf("Cos 30 %f\n", cos_from_deg(30));
    printf("Cos 45 %f\n", cos_from_deg(45));
    printf("Cos 60 %f\n", cos_from_deg(60));
    printf("Cos 90 %f\n", cos_from_deg(90));
    printf("Cos 110 %f\n", cos_from_deg(110));
    printf("Cos 150 %f\n", cos_from_deg(150));
    printf("Cos 180 %f\n", cos_from_deg(180));
    printf("------------\n");
    printf("Cos 0 %f\n", cos_from_deg(0));
    printf("Cos -30 %f\n", cos_from_deg(-30));
    printf("Cos -45 %f\n", cos_from_deg(-45));
    printf("Cos -60 %f\n", cos_from_deg(-60));
    printf("Cos -90 %f\n", cos_from_deg(-90));
    printf("Cos -110 %f\n", cos_from_deg(-110));
    printf("Cos -150 %f\n", cos_from_deg(-150));
    printf("Cos -180 %f\n", cos_from_deg(-180));
    return 0;
}