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Trigonometry missing?


 
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# 8  
Old 07-22-2011
On the contrary, your math.h is complete (there's a standard, after all, what has to be provided). If you use a function that's not defined, you'd get a warning about an "implicit declaration". But as pflynn said above: you have to explicitly link the math library, using the -lm switch.
# 9  
Old 07-22-2011
OK now it works...I must link libm with -lm
gcc trig.c -lm -o trig

Is this kind of trig faster than using a table?
I have seen that some routines for FFT are using a table with sin/cos data.
# 10  
Old 07-22-2011
So, I was right:

Quote:
(...)most of the questions related to the use of the GNU Libc mathematical funcions have to do with linking time problems. To compile and link programs that use the functions from the mathematical library, you need to explicitly tell gcc (or g++) to link your program agaist the library(...)

Code:
gcc -o trig trig.c -lm

# 11  
Old 07-22-2011
Quote:
Originally Posted by Pelle-48
Is this kind of trig faster than using a table?
A table would have fantastic speed but very poor accuracy; the lilbrary routines are built for maximum accuracy on the assumption they may be put to scientific or mathematical use.

If you'd posted what your error message was in the first place we could have solved your problem in one post instead of two pages.

Last edited by Corona688; 07-22-2011 at 03:14 PM..

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