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Create Arc with 2 Tangents help (#2676)
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blowlamp  
#1 Posted : Friday, November 27, 2009 5:50:48 AM(UTC)
blowlamp

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Joined: 6/28/2008(UTC)
Posts: 648
I'm attempting to create an arc that is tangent to a circle and a straight line. I have attached a picture to help explain what I need. The arc shown in purple must be tangent to the black line at the point where the blue line intersects with it - this is no problem as I'm using the Tangent Points Arc tool. What I can not achieve is tangency between the red circle and the purple arc. The radius of the purple arc is not known and doesn't matter, it just needs to be tangent to the red circle and the black line. I feel I'm missing something simple here but I just can't work it out. Does anyone have a solution to this?

Thanks.
Martin.
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arctangent.jpg (25kb) downloaded 4 time(s).

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zumer  
#2 Posted : Friday, November 27, 2009 10:42:43 AM(UTC)
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Martin: Draw a line normal to the tangent definer from the intersection point. To be tangential to the line at the intersection, the arc's centrepoint will be along a normal from there. Mirror the circle about the normal line, then fit a 3-tangent-point circle to the line and the two circles, then trim to the circle and line.
zumer attached the following image(s):
tangential solution.PNG (12kb) downloaded 4 time(s).

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blowlamp  
#3 Posted : Friday, November 27, 2009 12:26:56 PM(UTC)
blowlamp

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Thanks, Zumer. That worked well:). Much appreciated.

Martin.
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Tim Olson  
#4 Posted : Thursday, August 26, 2010 10:04:25 AM(UTC)
Tim Olson

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>>I'm attempting to create an arc that is tangent to a
>>circle and a straight line.

Martin

Some progress here in 947.

http://www.csi-concepts.com/Demo/videos/cirTan3.mov

Tim
Tim Olson
IMSI Design/Encore
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blowlamp  
#5 Posted : Thursday, August 26, 2010 12:17:57 PM(UTC)
blowlamp

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Posts: 648
Oh yes!! Thanks, Tim and Co.

Martin.
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blowlamp  
#6 Posted : Thursday, February 17, 2011 3:42:19 PM(UTC)
blowlamp

Rank: Senior Member

Joined: 6/28/2008(UTC)
Posts: 648
I've done a video and near the beginning, it shows the Tangent Points Arc tool in use to make an ark that is tangential to both the green line and the circle.

You can see that if there was a Tangent Snap option on the third click of this tool, then it would be very easy to make a neat arc.

The second part of the video shows how I'm doing this job at the moment, but it would be much easier with the Tangent option enabled.


Martin.

http://www.screencast.com/users...e-41ef-8a20-9af7119117d3
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NickB  
#7 Posted : Thursday, February 17, 2011 4:02:38 PM(UTC)
NickB

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Martin,
Good screencast.

Something that simple should not be so difficult and require such an ingenious work around.
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