we know cos is even
| 73 | |
| 74 | //we know cos is even |
| 75 | float CosF(float X) |
| 76 | { |
| 77 | INTN Period; |
| 78 | float Sign = 1.0f; |
| 79 | float X2; |
| 80 | |
| 81 | if (X < 0.0f) { |
| 82 | X = -X; |
| 83 | } |
| 84 | Period = (INTN)(X / PI2); |
| 85 | X = X - Period * PI2; |
| 86 | if (X > PI) { |
| 87 | X = PI - X; |
| 88 | Sign = -1.0f; |
| 89 | } |
| 90 | if (X > PI5) { |
| 91 | X = PI - X; |
| 92 | Sign *= -1.0f; |
| 93 | } |
| 94 | if (X > PI * 0.25f) { |
| 95 | return (Sign*SinF(PI5 - X)); |
| 96 | } |
| 97 | X2 = X * X; |
| 98 | return (Sign * (1.0f - X2 * 0.5f + X2 * X2 / 24.0f)); |
| 99 | } |
| 100 | |
| 101 | float TanF(float X) |
| 102 | { |