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Sine, cosine, tangent.

Posted on 1998-10-01
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Last Modified: 2012-08-13
I would like to calculate the sine cosine and tangent of some numbers.  What are the functions that let me to do that?  I am new to C++ and English so please be clear.  Thank you.
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Question by:theperson
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by:theperson
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Edited text of question
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by:thresher_shark
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Here are the names of the functions that do what you ask:
sin
cos
tan

For the arc sine, arc cosine, and arc tangent look into:
asin
acos
atan

All of these functions are declared in the "math.h" header file, so make sure you add:

#include <math.h>

to the top of your source code.

Also, remember that the numbers you provide the function are in radians, not degrees.  To convert from degrees to radians, multiply the number of degrees by:
0.01745329252 (roughly)  :-)

Here's an example.

Let's say you want to calculate the sine of 234 (degrees).  You would use:

result = sin (234 * 0.01745329252);

Consider definining a constant double at the top of the source code that looks like:

const double DEG2RAD 0.01745329252;

or something like that.  That way, you don't have to remember those arcane numbers.

Here is an example that uses the DEG2RAD constant:

sin (234 * DEG2RAD);

See how much easier that is to read?

If you have any additional questions, please ask.
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by:Answers2000
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Thresher you mean
const double DEG2RAD = 0.01745329252;

Good answer otherwise

BTW the maths relies on 2 * PI radians in 360 degrees
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by:nietod
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thresher_shark, its bad enough that ozo doesn't ever answer, do you have too?  What is this world coming to?  Greed is the prime motivating force for progress, without it the universe will come to a screetching halt.  : - )
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by:Hippy
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If you plan on using these functions in anything fast, say graphics routines, realtime calculations etc.  Use them to make a lookup table first, then just referance the lookup table, this way you only have to caculate things once, at the start of your program.

Hippy.
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by:nietod
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Its often not worth it these days.  On a pentium, the transcental function can take as little as about 20 clock cycles and at worst about 150 clock cycles.  Your look-up code is likely to take longer than that.  It certainly isn't going to be much faster.
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by:daitt
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I think that it's enough for all of you to chat here. The text of Thresher is really a good answer, but if he didnot want to answer, I'll do. I want to stop this question.
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by:daitt
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I'm sorry, but my answer has push Thresher out. Here is his answer:

"
Here are the names of the functions that do what you ask:
sin
cos
tan

For the arc sine, arc cosine, and arc tangent look into:
asin
acos
atan

All of these functions are declared in the "math.h" header file, so make sure you add:

#include <math.h>

to the top of your source code.

Also, remember that the numbers you provide the function are in radians, not degrees.  To convert from degrees to radians, multiply the number of degrees by:
0.01745329252 (roughly)  :-)

Here's an example.

Let's say you want to calculate the sine of 234 (degrees).  You would use:

result = sin (234 * 0.01745329252);

Consider definining a constant double at the top of the source code that looks like:

const double DEG2RAD 0.01745329252;

or something like that.  That way, you don't have to remember those arcane numbers.

Here is an example that uses the DEG2RAD constant:

sin (234 * DEG2RAD);

See how much easier that is to read?

If you have any additional questions, please ask.
"
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by:nietod
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Well that's a useful answer that tells theperson so much that he/she didn't know.
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by:thresher_shark
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Answers2000 - You're right, careless mistake :-)  I have recently switched over from "#define"s to "const"s so I occasionally forget the '=' sign.

daitt - It is usually considered bad form to "answer" a question using someone else's comments.  I cannot use EE to the same extent that I used to be able to (only able to log on about once a day for half hour to hour) because I have school and a life.  That means it might take me some time to respond to comments.  Please see my profile.

nietod - I think I am going to go back to actually answering questions again.  I was just giving the "answer-in-comment" approach a try because it would keep the question open so the customer could get more response from other experts.  It's unfortunate that people "answer" the question with someone else's comment(s).
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by:thresher_shark
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theperson - Please select the "Reject" or "Re-open" current answer (I am not sure of the exact terminology) from your list of options.  It is separate from the rest of the buttons.
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by:theperson
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Everyone has been most helpful.  Thresher_shark: I have rejected the current answer.  Now what do us do?
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by:Answers2000
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theperson - wait for Thresher to post a dummy answer, then grade that
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thresher_shark earned 200 total points
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Thank you very much.  If you have any further questions regarding my answer, please feel free to ask them.
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Author Comment

by:theperson
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No, there are no other questions about this, I have figured it all out now.  Thank you every one!
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