OJ Board

Tks, I have already founded it. abs() was in stdlib.h
and i just have atan() thats why I dont find that.

Hi! I have to use these fuctions arctan() and abs() but the compiler didnt find it in math.h . Is it in another library?

Is there a site that has a list of librarys and its functions?

I saw an error in my formula. I was using the midpoint to rotate, but ill never find the C point with this (i think). Then I changed the x,y coordinates of the rotation axis to the point B and the point that I want to rotate to A, rotating 60

I used the same way you showed this last post. At least when I used my way in your values I found the same C point.

But when I use in my program I get (6.710351,-6.710351).

The only thing that may be wrong then its the midpoint. What formula did you use to find it? I used (A+B)/2, maybe it is wrong.

angga888 wrote: x' = cos@ * (x-p) - sin@ * (y-q) + p
y' = sin@ * (x-p) + cos@ * (y-q) + q

I used this formula like this, see if its right:

I have A and B points and want to know the C

used x and y as valors of A
p and q valors of the midpoint of AB
and cos and sin of 90

Another dumb question... When in the problem says to divide AB in ratio of 1:3, you divided it in 3 or 4 pieces? And if I use (point A + the distance of the piece) I can get the point C?

How do you rotate de coordinates? I never heard of it.

Hi! Im having problems to discover the points of the equilateral triangle. Someone can help me with how can I draw this triangle?

Tks

sry, wrong problem

Hi! Im having problems to discover the points of the equilateral triangle. Someone can help me with how can I draw this triangle?

Tks