Roger Hui wrote: > It is false that (sin +&*: cos) y not equal to 1 > implies that sin y or cos y or both are wrong. >
Here's a floating-point example: u=:0.17211988309608894 1=!.0 (cos +&*: sin) u 0 If c and s are estimates for cos(y) and sin(y) with error less than e, where e^2 is negligible, (c +&*: s) is an estimate for 1 with error less than 2*e*(cos(y)+sin(y))<:e*2^3r2. So even if c and s are accurate to 1 ULP, there is no guarantee that (c +&*: s) will be. I would not trust those ephemerides for space travel. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
