Find Perpendicular Lines Meet on Line

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wildspidee
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Find Perpendicular Lines Meet on Line

Post by wildspidee » Fri Jan 09, 2015 4:30 pm

I am converting hand pattern drafting instructions to work in QCAD. I've come up against something that I simply can't figure out. Please see the attached drawing. I apologize for the quality, it comes from an old book.

In the hand drafting instructions, you are supposed to put a square with one side on point "O" and the other side on Point "P" and rotate/slide the square until it touches the line "N". This new point is the "Q". Thus O-Q and P-Q are perpendicular.

I tried creating a virtual "square" in QCAD and rotating it with no success. You've always come to my rescue in the past, I sure hope you have a solution for this one.

Thank you for your time.
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Square.jpg
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andrew
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Re: Find Perpendicular Lines Meet on Line

Post by andrew » Fri Jan 09, 2015 4:38 pm

Could you post screen shots of what the drawing looks like at first and what the solution should look like (approximately, if you cannot construct it)? Thanks.

wildspidee
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Re: Find Perpendicular Lines Meet on Line

Post by wildspidee » Fri Jan 09, 2015 4:51 pm

Here is a before and an after. The magenta lines are the "square". As you can see, they are not even close to perpendicular, but you get the idea. I put the point letters in to help clarify to the original image.

I've also included the entire file, if you want to play with it.

Thank you.
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DraftBodice.dxf
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DrawingFinish.jpg
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DrawingStart.jpg
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andrew
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Re: Find Perpendicular Lines Meet on Line

Post by andrew » Fri Jan 09, 2015 5:22 pm

If I understand your problem correctly, you can use Thales' theorem:

- Draw > Circle > Two Points
- First point is P, second is O
- Intersection between circle and line N is Q
Screen Shot 2015-01-09 at 17.21.15.png
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wildspidee
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Re: Find Perpendicular Lines Meet on Line

Post by wildspidee » Fri Jan 09, 2015 6:01 pm

Andrew, your skills never cease to amaze me. Such a simple solution and it works perfectly. I really appreciate your time on this.

By the way, I've gotten quite a large audience over on YouTube and I'm about to tell them all they need to buy QCAD Pro. I hope this generates some income for you to offset your time answering all my questions. I'm also contemplating a plugin for QCAD Pro, that I will release for free. They'll have to buy your software to use it.

Thanks again,
Lori

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andrew
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Re: Find Perpendicular Lines Meet on Line

Post by andrew » Fri Jan 09, 2015 6:26 pm

wildspidee wrote:Andrew, your skills never cease to amaze me. Such a simple solution and it works perfectly. I really appreciate your time on this.
No problem.
wildspidee wrote:By the way, I've gotten quite a large audience over on YouTube and I'm about to tell them all they need to buy QCAD Pro. I hope this generates some income for you to offset your time answering all my questions. I'm also contemplating a plugin for QCAD Pro, that I will release for free. They'll have to buy your software to use it.
That sounds great, thanks!
If you need any help with the plugin, let us know over at Developers and Contributors.

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