Consider for a second the range of the tangent function.  It ranges from -Infinite to +Infinite, and a large portion of the range is between -1 and 1.  If we were to ignore the *256, and simply take the ratio of Sin(angle)/Cos(angle), our function would return 0 for that portion of the range, as Axe cannot represent fractional numbers.  Obviously this is highly undesirable, so before we divide, we multiply by 256.  This is what is known as 8.8 fixed point notation.  In 8.8 fixed point, 256 is treated as 1, and this way, we can represent fractional numbers.  128 for example would represent 0.5.