SinTables.h

// from https://forum.arduino.cc/index.php?topic=69723.0 with thanks
// only skimmed before i yoinked, might be a faster/more accurate version in the thread

#ifndef SINTABLES_INCLUDED
#define SINTABLES_INCLUDED TRUE

// 91 x 2 bytes ==> 182 bytes
unsigned int isinTable16[] = {
 0, 1144, 2287, 3430, 4571, 5712, 6850, 7987, 9121, 10252, 11380,
 12505, 13625, 14742, 15854, 16962, 18064, 19161, 20251, 21336, 22414,
 23486, 24550, 25607, 26655, 27696, 28729, 29752, 30767, 31772, 32768,

 33753, 34728, 35693, 36647, 37589, 38521, 39440, 40347, 41243, 42125,
 42995, 43851, 44695, 45524, 46340, 47142, 47929, 48702, 49460, 50203,
 50930, 51642, 52339, 53019, 53683, 54331, 54962, 55577, 56174, 56755,

 57318, 57864, 58392, 58902, 59395, 59869, 60325, 60763, 61182, 61583,
 61965, 62327, 62671, 62996, 63302, 63588, 63855, 64103, 64331, 64539,
 64728, 64897, 65047, 65176, 65286, 65375, 65445, 65495, 65525, 65535,
 };

// 91 bytes
uint8_t isinTable8[] = {
 0, 4, 9, 13, 18, 22, 27, 31, 35, 40, 44,
 49, 53, 57, 62, 66, 70, 75, 79, 83, 87,
 91, 96, 100, 104, 108, 112, 116, 120, 124, 128,

 131, 135, 139, 143, 146, 150, 153, 157, 160, 164,
 167, 171, 174, 177, 180, 183, 186, 190, 192, 195,
 198, 201, 204, 206, 209, 211, 214, 216, 219, 221,

 223, 225, 227, 229, 231, 233, 235, 236, 238, 240,
 241, 243, 244, 245, 246, 247, 248, 249, 250, 251,
 252, 253, 253, 254, 254, 254, 255, 255, 255, 255,
 };


float isin(long x)
{
 boolean pos = true;  // positive - keeps an eye on the sign.
 if (x < 0)
 {
   x = -x;
   pos = !pos;  
 }  
 if (x >= 360) x %= 360;  
 if (x > 180)
 {
   x -= 180;
   pos = !pos;
 }
 if (x > 90) x = 180 - x;
//  if (pos) return isinTable8[x] * 0.003921568627; // = /255.0
//  return isinTable8[x] * -0.003921568627 ;
 if (pos) return isinTable16[x] * 0.0000152590219; // = /65535.0
 return isinTable16[x] * -0.0000152590219 ;
}

float icos(long x)
{
 return isin(x+90);
}

float itan(long x)
{
 return isin(x) / icos(x);
}

float fsin(float d)
{
 float a = isin(d);
 float b = isin(d+1);
 return a + (d-int(d)) * (b-a);
}

#endif