.ACT FOR I%, 0, 31 EQUB INT((128 / PI) * ATN(I% / 32) + 0.5) NEXTName: ACT [Show more] Type: Variable Category: Maths (Geometry) Summary: Arctan table Deep dive: The sine, cosine and arctan tablesContext: See this variable in context in the source code References: No direct references to this variable in this source file

To calculate the following: theta = arctan(t) where 0 <= t < 1, look up the value in: ACT + (t * 32) The result will be an integer representing the angle in radians, with 256 representing a full circle of 2 * PI radians. The table does not support values of t >= 1 or t < 0 directly, but we can use the following calculations instead: * For t > 1, arctan(t) = 64 - arctan(1 / t) * For t < 0, arctan(-t) = 128 - arctan(t) If t < -1, we can do the first one to get arctan(|t|), then the second to get arctan(-|t|).