Fast and Accurate Trigonometric Functions on the HP-17BII « Next Oldest | Next Newest »

 ▼ Gerson W. Barbosa Posting Freak Posts: 2,761 Threads: 100 Joined: Jul 2005 01-12-2007, 05:31 PM To all who might be interested, just available at the Articles Forum: Accurate? Surely! Fast? Well, kind of. But I wanted to make up a trilogy :-) Thanks Charles for first noticing the simpler equations were better. Regards, Gerson ▼ Karl Schneider Posting Freak Posts: 1,792 Threads: 62 Joined: Jan 2005 01-14-2007, 01:25 AM Hi, Gerson -- Thank you for posting your dedicated work in the Articles Forum. They are certainly worthy, and probably more appropriate there than in the Software Library, due to the applied-mathematics content. I expect that the HP-17BII programs will work on the HP-17B, as well? Regards, -- KS ▼ Gerson W. Barbosa Posting Freak Posts: 2,761 Threads: 100 Joined: Jul 2005 01-14-2007, 02:37 AM Hello Karl, I don't have an HP-17B but I think the equations should run just fine on it. I'd like to test the equations on the HP-17BII+ also. The HP-200LX was a good developing tool, but when solving for the inverse functions using the full-range equations I noticed the HP-17BII behaved differently. That's why I had to append the apparently useless terms to the cosine and tangent equations in the what I called IF-LESS EQUATIONS sets (that was an experiment I decided to keep). I have just included a note at the end about a even shorter minimax polynomial equation (see my reply to Charles, which ended up orphan). The minimax polynomial is accurate in the range -18 to 18 degrees, that is, +/- 90/5. It is then expanded to -90 to 90 degrees by means of ``` sin 5.x = sin x * (sin2x * (16 * sin2x - 20) + 5) ``` This doesn't improve the solving time but makes the equation shorter. Reducing the range even more would actually make the equation slower and longer. I think this is the right balance between size and speed. Regards, Gerson. Edited: 14 Jan 2007, 2:38 a.m.

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