Included angle for a segment of circle

[ProfWolfMan]

Hi,

I am trying to find included angle for a circle segment.
See attached image.(i need to find ang2).
all other yellow marked values are i have.
Below is my code. But result is not correct.
Whats wrong with my code? any idea?
-----------------------------------------------------------
Dim P1 As Point2d = New Point2d(0, 0)
Dim Pt1 As Point2d = Util.PolarPoint(P1, ang1, r)
Dim Pt2 As Point2d = Util.PolarPoint(Pt1, ang1 + 90, d / 2)
Dim Pt3 As Point2d = Util.PolarPoint(Pt1, ang1 - 90, d / 2)
Dim acV1 As Vector2d = dblOrginPt.GetVectorTo(Pt2)
Dim acV2 As Vector2d = dblOrginPt.GetVectorTo(Pt3)
Dim ang2 As Double = acV1.GetAngleTo(acV2)
-----------------------------------------------------------

note: i didn't follow any coding std for above piece of code.
please excuse me for that.

Thanks & regards,
g

[cadMeUp · Accepted solution]

I believe the PolarPoint method of the AcadUtility object expects the angle parameter to be in radians:

Dim rad90 As Double = Math.PI / 2

Dim Pt2 As Point2d = Util.PolarPoint(Pt1, ang1 + rad90, d / 2)

Dim Pt3 As Point2d = Util.PolarPoint(Pt1, ang1 - rad90, d / 2)

also make sure that the ang1 var is in radians.

I didn't test your code though, hopefully that will get it working correctly.

[ProfWolfMan]

Hi,

You are correct.
That polarpoint method in my util class requires angle in radians.

Now everything is working fine.

Thank you very much for your timely help

Regards
G

[cadMeUp]

Also, if you are just getting the points to calculate the angle you can avoid the PolarPoint method. As long as you know the radius and the offset distance you can use a little trig to calculate the angle:

Dim r As Double = 10
Dim d As Double = 4

'Get one half of the needed angle, in radians
Dim halfAngRad As Double = Math.Atan(1 / (r / (d / 2)))

'Convert the half angle to degrees
Dim halfAng As Double = (halfAngRad / Math.PI) * 180

'To get the total angle in degrees multiply by 2
Dim incAng As Double = halfAng * 2

incAng will equal 22.6198649480404

and you could combine them into one statement:

Dim incAng As Double = ((Math.Atan(1 / (r / (d / 2))) / Math.PI) * 180) * 2

[ProfWolfMan]

Hi,

That is great!

I always forgot about geometrical ideas to find solution when i am doing program! that's shame for me.

Thank you very much for your valuable guidance.

I really very much like this discussion board where i can find all the answers from these huge discussions.

Thanks all genius to share their knowledge here.

Regards,

G