🚀 go-pugleaf

ryangall@gpu.srv.ualberta.ca (Bobby Sixkiller) wrote:

>I am working on a computer program in c, and I need to find the angle of a 
>given line. I have access to a tan() function which takes an angle, and 
>returns the tan of that angle. The problem I'm facing is that I have 
>the tan of the angle already(opposite and adjacent values) but dont know 
>what the angle is.. thats what I want to find. I know that on a calculator 
>I could just go tan ^-1 opposite/adjacent to get the angle, but I dont 
>have acces to an inverse of tan function. Can I get the inverse of tan by 
>using only the tan() function and the opposite and adjacent 
>values.....please mail me any ideas!

Well, you might just brute force each one, depending on how time
critical the thing is. Something like:

float arctan(float y)
{
  float x;
  x=0;
  while (tan(x)<y) do x=x+0.01;
  return x
}

That'll do for up to pi, or 90 degrees, with .01 accuracy, but it will
be slow.  You could make it a lot faster, (10x actually) by making the
increment only .1.  If you have an arcsin function, you could use it
to calculate arctan I think...

 - Executioner/[Independent]
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