▼ JuanMi Unregistered Posts: 9 Threads: 2 Joined: Jan 1970 09-29-2004, 07:20 AM Dear HP Gurus :), I have recently purchased on ebay an HP28S (at last!!!!) which works fine but unfortunately with no owner manuals. My question is: I have to work with very simple vectors calculations (speed and course of a ship added to speed and course of a stream/tide) and I get "strange" results from my HP28S (sure, I'm doing something wrong). Let's show a very simple (and quite stupid, I know!) example: Speed of ship: 10 kts. Ship Course: 0 degrees (north) stream speed: 5kts. stream course/direction: 180 degrees (south). Of course, anybody needs a calculator for this example!!!. Resulting vector is: (5,0). So, real speed 5 kts, real course 0 deg (no changes). Ok, but when I do the vector summation, I get: (15,180) My inputs: (10,0) as first vector (5,180) as second vector + (addition) (15,180). On my Hp48GX needed to change to cyl coordinates... What am I doing wrong?... any advice will be highly appreciated. Inbetween, I look for a manual... Best regards and greetings from Spain!, JuanMi ▼ John Limpert Unregistered Posts: 172 Threads: 13 Joined: Jul 2005 09-29-2004, 09:08 AM The HP-28S does everything in rectangular coordinates. You need to convert your data to rectangular coordinates, do the mathematical operations, and convert the result back to polar coordinates. See the P->R and R->P keys on the CMPLX menu (press CMPLX NEXT). ▼ JuanMi Unregistered Posts: 9 Threads: 2 Joined: Jan 1970 09-29-2004, 10:12 AM Yeah! It worked. Thank you very much for the info... I did'nt realize... Best regards, JuanMi

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