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 Select a Forum     Round Tables New Member Discussions News Discussions Algorithm Matches Marathon Matches NASA Tournament Lab TopCoder Cookbook High School Matches Sponsor Discussions Development Forums Design Forums Search | Watch Thread  |  My Post History  |  My Watches  |  User Settings View: Flat (newest first)  | Threaded  | Tree Previous Thread  |  Next Thread Forums Tutorial Discussions Geometry Concepts Finding a signed angle
 Finding a signed angle | Reply Here is a better algorithm for finding a signed angle between two line segments with a common starting point where the angle is measured counter-clockwise from 0 to +/- pi.```double sX, sY; //the common starting point double aX, aY, bX, bY; //the two points radiating from sX,sY ... //using C# Math.Atan2(y,x) method: double dRad1 = Math.Atan2(aY-sY,aX-sX); double dRad2 = Math.Atan2(bY-sY,bX-sX); double dRad = dRad2 - dRad1; ```note: angles > pi are shown as (pi - angle)
 Re: Finding a signed angle (response to post by dran001) | Reply Trig way that I have an easier time remembering:```dRad = Math.atan2(Math.sin(dRad), Math.cos(dRad)); ```Probably faster way:```dRad = (dRad+Math.PI)%(Math.PI*2)-Math.PI; ```
 Re: Finding a signed angle (response to post by dran001) | Reply If aX == sX or bX == sX, then we would have a division by zero, right? What to do in this case?
 Re: Finding a signed angle (response to post by elcabezon) | Reply Note that atan2() takes two arguments: y and x, not one argument y/x. There is no division by zero. See man atan2 for more detail.
 Re: Finding a signed angle (response to post by misof) | Reply OK thanks
 Re: Finding a signed angle (response to post by misof) | Reply Is there a way to see the source code of these trigonometric functions? I've looked in /usr/include/math.h but I can't find it.
 Re: Finding a signed angle (response to post by wack-a-mole) | Reply `www.google.com/codesearch?q=\satan2\([^\)]*\)\s*{`edit: Just copy the whole link, I can`t get it to work on this forum.edit2: sorry, the results are not that good
 Re: Finding a signed angle (response to post by maniek) | Reply Still , We don't have actual code.
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