How to convert degrees to radians so that sine would work precisely?

Sorry, I hope you are coding in C/C++ BTW. :)

A more generic calculation (but not as computationally fast as for the case where sine=180 as Mathematix points out):

     const double epsilon = 1e-15;
     double val = sin(radians);
     if (fabs(expected-val) < epsilon) {
        val = expected;
     }

where radians, and expected are either defined earlier, or passed in to method/function.

-Jon

I made some calculations. The 30° answer isn't exactly 0.5 but
0,499999999999999999933223179531195
the 180° one is 4,6264338327950288419718286668577e-19
it's some 18 zeroes after "0," awfully precise, but still —
for example when player rotates about some axis thousands of times then there are only 14 zeroes and so on...
you'll have to do something like this:
ß>=pi => ß=0
ß<=-pi => ß=0
The precision will remain, but I still don't understand were you need that kind of precision.
NO calculator will find that sin(30)=0.5, because they work with bits!
There is always possibility to use look-up-tables, but it's slower when you have thousands of values stored, but it's your decision.
Hope it helps

Thanks to all you folks who have replied to my question providing various tips on how to solve the problem.

It looks like I am going to use the sine function even if it does not return precise numbers. It's true that I don't need such a precision as you have pointed out - the sine function is used to calculate the camera position after a move in the given direction. I will probably choose a way of rounding the number to a finite number of decimal digits so the imprecisions will get smoothed.

I just posted this question here because I was confused by the fact that I am not able to calculate the sine of 180 degrees as a precise zero as it should be. I thought I had to be making something badly or using an incorrect method for converting degrees to radians... I thought that there just had to be a certain value of pi that the sin() function itself used and that if I had fond this value, the function would return precise 0 as it was supposed to do. Perhaps I am not able to fully appreciate the power of radians now, but I still think that if the VC++ mathematic functions used degrees rather than radians, the work would be much more convenient as it would be sure that sin(180)==0 etc. and you would not have to spend time doing the conversions back and forth.

If you have any other ideas guys, I am willing to listen, as I have almost no expertise at this field (being a programmer in general for already eight years, however) and I am a high school sophomore student, so do not know as much about maths as you here do.

And yet another question: I am a newbie to this site (Experts-Exchange). Could you please tell me whether I should give the 50 points I have assigned to this question to anyone of you (who?) or should I keep it as noone of you has posted their question as a question, only as a comment?

Thanks in advance.
Marek

Correction: In the last paragraph I meant "noone of you has posted their question as an answer" - rather than "as a question".

blahma, et. al.,

I am also somewhat new to this site, but I do have an opinion on this topic.

As for awarding points, my suggestion is to do one of these things:

1. Look again carefuly at the responses to your question. Ask yourself if one particular comment helped you to either understand the question you were asking, or pointed you in the right direction. If this is the case, then award the points to that person;

2. If the above isn't the case, I favour awarding points to people who tried, and supplied help and information. I suggest awarding some points to each person you felt contributed in an informative way. According to DanRollins, you can award points to any expert by this mechanism:

   "To give points to an Expert, ask a new question in the same Topic Area.  Title it "Points for XxxXxxxxxx" and (this is important) in the body of the question, provide a link to *this* question."

Jongoldifsh says: Here is a link to this question, so you can cut-and-paste:

http://www.experts-exchange.com/Programming/Game_Development/3D_Programming/Q_20453557.html

(information on how to award points to an expert borrowed from Dan Rollins at question: http://www.experts-exchange.com/Programming/Programming_Languages/Cplusplus/Q_20443597.html)


Hope this helps,
-Jon..goldfishy

Oh yeah, one other thing-- I think that if you do elect option 2 as I describe above, there is some way "official" way to cancel/cleanup your question. But then I suggest you go to the "Community Support >> CleanUp" area and ask them to do it, or to explain how, or read through the various questions&faqs on this site.

-Jon..goldfishy