## 3 point arc

Moderator: andrew

### 3 point arc

How can I draw a 3 point arc tangentially from an arc say.... on the left , down to a line and then tangentially to one on the right ? You can see (hopefully my previous attempt and you should see that the circle on the left is not tangential with the arc. All help gratefully received . Thank you .
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30tooo
Newbie Member

Posts: 5
Joined: Wed Nov 23, 2011 11:56 am

### Re: 3 point arc

If you look at my picture you will see a line atvthe bottom. The was another parallel to that. That is a restriction. I used 3 point arc but if you look close you will see it is not tangential to the left circle. I thought i might be able to snap tangentially , snap to object ( the line) and the tangentially to the right circle.

I hope i have explained that ok.

30tooo
Newbie Member

Posts: 5
Joined: Wed Nov 23, 2011 11:56 am

### Re: 3 point arc

Thanks for being patient Clive . Maybe this might help you understand .
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30tooo
Newbie Member

Posts: 5
Joined: Wed Nov 23, 2011 11:56 am

### Re: 3 point arc

30tooo
Newbie Member

Posts: 5
Joined: Wed Nov 23, 2011 11:56 am

### Re: 3 point arc

30tooo wrote:I thought i might be able to snap tangentially , snap to object ( the line) and the tangentially to the right circle.

Unfortunately that isn't possible in the moment - but I know that the developers are working on it for one of the next updates
Right now you have to work with construction / help lines to solve this challenge.

Husky
Moderator/Drawing Help/Testing

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Joined: Wed May 11, 2011 9:25 am
Location: USA

### Re: 3 point arc

Yes, this should fit the bill.

BTW: The tool for this use case is called "3 Tangents" (not "Point, 2 Tangents"), I think the wrong tooltip might have been displayed in the screenshot above.

andrew

Posts: 4011
Joined: Fri Mar 30, 2007 6:07 am

### Re: 3 point arc

I see.. which point did you choose then? Is the exact point on the line given or another point? I thought the circle touches the two other circles as well as the line.

andrew

Posts: 4011
Joined: Fri Mar 30, 2007 6:07 am

### Re: 3 point arc

clive wrote:I think Apollonius 'The Great Geometer' would have loved these circle tools.
Andrew you have done a fantastic job with these additional tools

Well, thanks It's a surprisingly complex problem. QCAD is using resizing and inversion to find the solutions.

andrew

Posts: 4011
Joined: Fri Mar 30, 2007 6:07 am

### Re: 3 point arc

clive wrote:Andrew you have done a fantastic job with these additional tools

WOW - what a circle tool set!!! I have absolutely to agree with Clive - that is an extraordinary tool-set.

@Andrew:
My honest respect and compliment to you!!! Thank you very much to make the "CAD life" so easy for everybody!

Husky
Moderator/Drawing Help/Testing

Posts: 1144
Joined: Wed May 11, 2011 9:25 am
Location: USA