## constructing a round using a circle with two tangential points

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Krischu
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### constructing a round using a circle with two tangential points

Bildschirmfoto 2019-09-17 um 10.44.08.png (180.35 KiB) Viewed 4649 times
How would I construct the small left circle. In this drawing it is just drawn so lá lá, not precisely constructed

One point is the endpoint of the line. The other two points are the tangent points of the two lines against the circle.
(N.B. the radius isn't known beforehand and the tangent points aren't either as well).
--
Christoph

TSG
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### Re: constructing a round using a circle with two tangential points

Thomas
Last edited by TSG on Tue Sep 17, 2019 11:39 am, edited 1 time in total.
Ich will nicht streiten. Ich will nur deutlich machen, dass ich Recht habe und DU NICHT.

CVH
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### Re: constructing a round using a circle with two tangential points

You could draw a vertical construction line at the endpoint and use 3 tangent.

andrew
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### Re: constructing a round using a circle with two tangential points

Draw > Circle > 2 Tangents and Point:

Krischu
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### Re: constructing a round using a circle with two tangential points

andrew wrote:
Tue Sep 17, 2019 12:39 pm
Draw > Circle > 2 Tangents and Point:
This doesn't seem to work. I'm asked for first line or circle, second line or circle and when being asked for "point on circle line" it doesn't snap at the endpoint.

@CVH: 3 Tangent works.

Thanks
--
Christoph

Krischu
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### Re: constructing a round using a circle with two tangential points

TSG wrote:
Tue Sep 17, 2019 11:31 am
Thomas
What were you going to tell me?
--
Christoph

Husky
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### Re: constructing a round using a circle with two tangential points

Krischu wrote:
Tue Sep 17, 2019 1:06 pm
This doesn't seem to work. I'm asked for first line or circle, second line or circle and when being asked for "point on circle line" it doesn't snap at the endpoint.
The CT2 tool is built to solve the task easily without auxiliary lines.

Try this click order:

Husky-2019.09.17-02.png (40.3 KiB) Viewed 4615 times
If it still not snap to the endpoint doublecheck your Auto Snap settings. End Points should be checked:

Husky-2019.09.17-03.png (22.58 KiB) Viewed 4615 times
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CVH
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### Re: constructing a round using a circle with two tangential points

Husky wrote:
Tue Sep 17, 2019 8:08 pm
Krischu wrote:
Tue Sep 17, 2019 1:06 pm
This doesn't seem to work. I'm asked for first line or circle, second line or circle and when being asked for "point on circle line" it doesn't snap at the endpoint.
The CT2 tool is built to solve the task easily without auxiliary lines.
Try this click order:
Sorry, but when your point is at the bissectrice there is no solution....
And that should be the easiest one, one only!
Last edited by CVH on Mon Sep 30, 2019 8:46 am, edited 2 times in total.

TSG
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### Re: constructing a round using a circle with two tangential points

I agree. In this case with QCAD 3.23.0.0 and macOS Mojave the tool ct2 doesn't work.
When snapping to the endpoint or any other point on the line all solutions disappear.
I think it's a bug.

Thomas
Ich will nicht streiten. Ich will nur deutlich machen, dass ich Recht habe und DU NICHT.

Husky
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### Re: constructing a round using a circle with two tangential points

Interesting!

Guys - please do me a favor: After you mentioned it doesn't works (and it was flawless working for me!) I tested a bit and discovert something interesting. I won't tell you now the result ....

This dxf has two identical situation. Please test on each on them what I posted as solution for this task and tell me how it works for you. Thanks.

CT2.dxf
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TSG
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### Re: constructing a round using a circle with two tangential points

#1 doesn't still work (no solution)
#2 works as expected (found 2 solutions)

Couldn't found any difference between the situations.
What's the reason for that?

Thomas
Ich will nicht streiten. Ich will nur deutlich machen, dass ich Recht habe und DU NICHT.

Krischu
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### Re: constructing a round using a circle with two tangential points

macOS mojave 10.14.6

Invoking ct2 on example 1. results in the solution circles disappearing when selecting the endpoint (3.)
Bildschirmfoto 2019-09-18 um 09.22.41.png (18.27 KiB) Viewed 4563 times
Doing the same on example 2. results in showing the two circles for choice end lets choose the desired solution circle:
Bildschirmfoto 2019-09-18 um 09.21.39.png (22.47 KiB) Viewed 4563 times
--
Christoph

TSG
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### Re: constructing a round using a circle with two tangential points

It's getting warmer...

When moving #1 down CT2 works.

Thomas
Ich will nicht streiten. Ich will nur deutlich machen, dass ich Recht habe und DU NICHT.

Husky
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### Re: constructing a round using a circle with two tangential points

Thanks for testing!
TSG wrote:
Wed Sep 18, 2019 9:06 am
Couldn't found any difference between the situations.
Both situation are exactly the same (copy). Difference is only the location.

CT2 behaves differently simply based on where it is used. Thomas, you expected already a bug - will you file a bug report?
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CVH
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### Re: constructing a round using a circle with two tangential points

Flaw depends on order reference line selection and selection place.
Flaw never 1 unique on bissectrice.
Flaw regions 0 instead of 2, 1 instead of 2 (drew quick and dirty).
Regions not strickt. Very tiny diffs may comply or not.

Regards,
CVH
Attachments
CT2_tested.dxf