Vectors addition on HP28S

[JuanMi]

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]

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]

Yeah!

It worked. Thank you very much for the info... I did'nt realize...

Best regards,

JuanMi