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1-Newbie

## Define angle from polar vector?

Hello

Once again a silly interface question: I have a vector in polar form. Now I could easily write down the real and the imaginary values down go on from there but I want to be able to define the angle of the vector so that I can use that angle later on. However I can not find a MathCad feature or some neat trick to get that angle defined. I have attached a picture with an example to show you what I mean.

I hope one of you have a neat solution. I use MathCad 3.1 by the way.

Best regards
Emil

9 REPLIES 9
16-Pearl
(To:emürer)

Alan

1-Newbie
(To:AlanStevens)

Hello Alan

I thought about that but then i would have to be able to define the real and imaginary number as B and A in order to use that calculation and i also cannot find a way to define those?

Emil

21-Topaz II
(To:emürer)

24-Ruby V
(To:-MFra-)

Your "Hypo" would yield wrong results for negative values of a because you use atan and not atan2.

Furthermore I wonder as of the complicated way you define this function. Guess that

Hypo(a,b):= a + b *1i

would do the very same jobin a clearer way and more convenient!

As far as I understood the question, Emil was asking for a way to "get hold" on the angle, to store it in a variable and not just to display it, Thats the reason I suggested the usage of "arg" or "atan2" as two ways to achieve this goal in my answer below.

Werner

21-Topaz II
(To:Werner_E)

Thanks Werner,

did not know of the existence of atan2.

In reality, however, no one would dream of defining the measures of the sides of a triangle with negative values ...

24-Ruby V
(To:-MFra-)

atan2 is not only available in Mathad, its also a function available in most programming languages.

 F.M. wrote: In reality, however, no one would dream of defining the measures of the sides of a triangle with negative values ...

triangle? Emil was speaking of "vectors" - obviously in the context of complex numbers, as he wrote about "real and the imaginary values" . So why shouldn't the real part of his complex number be negative? At least thats how I understood his question - how to calculate (and store for later use) the phase/argument/"angle" of a complex number.

But Emils question wasn't quite clear and his answer to Alan even more cryptic (at least to me). Seems that he dosn't show much interest anymore on this subject anway.

21-Topaz II
(To:Werner_E)

Hi Werner, I apologize, In reading your answer, I thought, absently, to the corresponding geometric figure and no longer at the vectors, as it was requested.

atan2, although I have studied in the second half of the last century, during my university studies in the course of programming in FORTRAN, and then, in more recent years when I developed the software in C ++, is a function that I have never used, even in MATHCAD, if I remember rightly.

Bye

FM

24-Ruby V
(To:emürer)

Hope this helps:

9-Granite
(To:emürer)

Hi.

You have also the Graphing functions pol2xy and xy2pol

Best regards.

Alvaro.

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