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macOS Issue calculating an angle (C)

M

mac2x

macrumors 65816
Original poster
Sep 19, 2009
1,146
0
I'll be up front and tell you guys that this is part of an assignment, but I'm only asking about this one thing that has been giving me fits for the past hour.

Basically, in the context of a larger problem, I need to calculate an angle; specifically by taking the arcsine of 2/3:

Code: 
theta = asin (2/3);

That is what I am attempting to use, but it is evidently incorrect in some way because the output claims theta is 0.000000 (theta is of type double). FWIW, I have initialized the variable theta to 0 on the suggestion of my instructor.

[edit] I checked the syntax and it seems right, but surely I am missing something. Let me know if you want the entire program.

Thanks for helping a novice programmer who is feeling like a noob! :D
 
M

mac2x

macrumors 65816
Original poster
Sep 19, 2009
1,146
0
Figured it out!

Boy do I ever feel dumb. :D

I did this problem on paper before translating it into C...and I got a little too gung-ho on copying. That 2/3 is SUPPOSED to be the quotient of two variables of type double that have been previously calculated by the program.

I have a feeling this will work better once I correct that issue. :)
 
T

timbos

macrumors member
Jan 2, 2009
34
0
Teddy Bear Debugging

One of my colleagues has a teddy bear on his desk. Whenever he gets stuck at something that seems simple (and correct) to him, he explains it to the bear rather than bug one of us. 9 times out of 10, having to explain the problem out loud makes it clear what the solution is. :)
 
robvas

robvas

macrumors 68040
Mar 29, 2009
3,240
629
USA
Also, don't forget that the C math functions take arguments in radians, not degrees

radians = degrees * (180/pi)
 
M

mac2x

macrumors 65816
Original poster
Sep 19, 2009
1,146
0
timbos said:
One of my colleagues has a teddy bear on his desk. Whenever he gets stuck at something that seems simple (and correct) to him, he explains it to the bear rather than bug one of us. 9 times out of 10, having to explain the problem out loud makes it clear what the solution is. :)
Click to expand...

Haha, I don't have a teddy bear, but I can sometimes find someone on skype to bug in a similar fashion. :D

robvas said:
Also, don't forget that the C math functions take arguments in radians, not degrees

radians = degrees * (180/pi)
Click to expand...

LPZ said:
Maybe that should be (pi/180)? :)
Click to expand...

Yes, the conversion is degrees * (π/180). ;) And yes, I am aware that it needs radians. :)
 
M

mac2x

macrumors 65816
Original poster
Sep 19, 2009
1,146
0
Catfish_Man said:
Probably best to use the builtin constants for these things; M_PI for π, M_1_PI for 1/π, and so on.
Click to expand...

That sounds interesting, but we haven't covered that yet in class so I'd be nervous about using it. Could you explain further? Thanks. :)
 
robvas

robvas

macrumors 68040
Mar 29, 2009
3,240
629
USA
mac2x said:
That sounds interesting, but we haven't covered that yet in class so I'd be nervous about using it. Could you explain further? Thanks. :)
Click to expand...

http://www.cs.cf.ac.uk/Dave/C/node17.html

The math.h library defines many (often neglected) constants. It is always advisable to use these definitions:

HUGE -- The maximum value of a single-precision floating-point number.
M_E -- The base of natural logarithms (e).

M_LOG2E -- The base-2 logarithm of e.

M_LOG10E - The base-10 logarithm of e.

M_LN2 -- The natural logarithm of 2.

M_LN10 -- The natural logarithm of 10.

M_PI -- $\pi$.

M_PI_2 -- $\pi$/2.

M_PI_4 -- $\pi$/4.
M_1_PI -- 1/$\pi$.

M_2_PI -- 2/$\pi$.

M_2_SQRTPI -- 2/$\sqrt{\pi}$.

M_SQRT2 -- The positive square root of 2.

M_SQRT1_2 -- The positive square root of 1/2.

MAXFLOAT -- The maximum value of a non-infinite single- precision floating point number.

HUGE_VAL -- positive infinity.
 
chrono1081

chrono1081

macrumors G3
Jan 26, 2008
8,453
4,159
Isla Nublar
timbos said:
One of my colleagues has a teddy bear on his desk. Whenever he gets stuck at something that seems simple (and correct) to him, he explains it to the bear rather than bug one of us. 9 times out of 10, having to explain the problem out loud makes it clear what the solution is. :)
Click to expand...

This works! I've told problems to co-workers who hear me yelling at the computer (and they ask why) and by explaining something (that I know they don't understand) just by saying it outloud I solve it myself.

There is also the famous "Solved it in a dream" that happens to almost every programmer, where you think of a problem so long you end up dreaming about it and solve it.
 
lee1210

lee1210

macrumors 68040
Jan 10, 2005
3,182
3
Dallas, TX
chrono1081 said:
This works! I've told problems to co-workers who hear me yelling at the computer (and they ask why) and by explaining something (that I know they don't understand) just by saying it outloud I solve it myself.

There is also the famous "Solved it in a dream" that happens to almost every programmer, where you think of a problem so long you end up dreaming about it and solve it.
Click to expand...

Or the shower, or in the car, or playing a game, etc. Sometimes letting something simmer under the surface instead of pounding your head against it is what your brain needs.

-Lee
 
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