Topic: how to get Arc Length using Chord and Radius with c#

[nobody]

Okay...so I've tried to format it a few different ways but can't seem to get the formula right in c#

Anyone willing to share a method if you have one?

[nobody]

Nevermind... took the long route.

Got the vectors to the start and end and then subtracted to get my angle.

Code - C#: [Select]

1. Vector2d anglestart = pipe.Curve2d.Center.GetVectorTo(new Point2d(pipe.StartPoint.X, pipe.StartPoint.Y));
2. Vector2d angleend = pipe.Curve2d.Center.GetVectorTo(new Point2d(myinvloc.X, myinvloc.Y));
3. double theta = anglestart.GetAngleTo(angleend);
4. dist = pipe.Radius * theta;//arclength
5.  

[Kerry]

Just in case you want the result as a math solution :

Code - C#: [Select]

1. using System;
2.  
3.  
4. namespace ConsoleApplication2 {
5.     class Program {
6.         static void Main(string[] args) {
7.             double radius = 200;
8.             double chordLength = 200;
9.  
10.             double circumference = Math.PI * 2.0 * radius;
11.             double enclosedAngleRadians = AngleFromChord(radius, chordLength);
12.             double arcLength = ArcLengthFromChord(radius, chordLength);
13.  
14.  
15.             Console.WriteLine("Circumference: " + circumference);
16.             Console.WriteLine("Enclosed Angle Radians: " + enclosedAngleRadians);
17.             Console.WriteLine("Enclosed Angle Degrees: " + enclosedAngleRadians * (180.0 / Math.PI));
18.             Console.WriteLine("Arc Length: " + arcLength);
19.  
20.             Console.ReadKey();
21.         }
22.  
23.         /// <summary>
24.         /// Get the arc length from the radius and enclosed angle
25.         /// </summary>
26.         public static double ArcLengthFromAngle(double radius, double radians) {
27.             return radius * radians;
28.         }
29.         /// <summary>
30.         ///  Get the angle from the chordLength (only works for angles <= 180)
31.         /// </summary>
32.         public static double AngleFromChord(double radius, double chordLength) {
33.             return radius != 0.0 ? 2.0 * Math.Asin(chordLength / (radius * 2.0)) : 0.0;
34.         }
35.         /// <summary>
36.         ///Get the arc length from the radius and chordLength
37.         /// </summary>
38.         public static double ArcLengthFromChord(double radius, double chordLength) {
39.             if(radius == 0.0)
40.                 return chordLength;
41.  
42.             return ArcLengthFromAngle(radius, AngleFromChord(radius, chordLength));
43.         }
44.     }
45. }
46.  
47.  

[nobody]

Thank you Kerry!  I've needed this for a few items. Much appreciated

Just in case you want the result as a math solution :

Code - C#: [Select]

1. using System;
2.  
3.  
4. namespace ConsoleApplication2 {
5.     class Program {
6.         static void Main(string[] args) {
7.             double radius = 200;
8.             double chordLength = 200;
9.  
10.             double circumference = Math.PI * 2.0 * radius;
11.             double enclosedAngleRadians = AngleFromChord(radius, chordLength);
12.             double arcLength = ArcLengthFromChord(radius, chordLength);
13.  
14.  
15.             Console.WriteLine("Circumference: " + circumference);
16.             Console.WriteLine("Enclosed Angle Radians: " + enclosedAngleRadians);
17.             Console.WriteLine("Enclosed Angle Degrees: " + enclosedAngleRadians * (180.0 / Math.PI));
18.             Console.WriteLine("Arc Length: " + arcLength);
19.  
20.             Console.ReadKey();
21.         }
22.  
23.         /// <summary>
24.         /// Get the arc length from the radius and enclosed angle
25.         /// </summary>
26.         public static double ArcLengthFromAngle(double radius, double radians) {
27.             return radius * radians;
28.         }
29.         /// <summary>
30.         ///  Get the angle from the chordLength (only works for angles <= 180)
31.         /// </summary>
32.         public static double AngleFromChord(double radius, double chordLength) {
33.             return radius != 0.0 ? 2.0 * Math.Asin(chordLength / (radius * 2.0)) : 0.0;
34.         }
35.         /// <summary>
36.         ///Get the arc length from the radius and chordLength
37.         /// </summary>
38.         public static double ArcLengthFromChord(double radius, double chordLength) {
39.             if(radius == 0.0)
40.                 return chordLength;
41.  
42.             return ArcLengthFromAngle(radius, AngleFromChord(radius, chordLength));
43.         }
44.     }
45. }
46.  
47.  

[Kerry]

You're welcome.

[Bryco]

Also     arc.GetFirstDerivative(arc.StartPoint) is the vector of the tangent at that point
arc.GetSecondDerivative(arc.StartPoint) is the vector of the radius