# How to draw a circle circumscribed and tanger to other two

#1

Hi everybody.

Not sure if I’m going to use the right English words to describe what I’m looking for.
My intention is to draw a circle circumscribed and tangent to other two.

Let’s suppose I have a circle called A and another one called B.
I’d like to know how I can find

1. the center of the arc I drew in “red/pink”
2. the tangent points of the big circle on A and B.

I know TIG developed an awesome extension called True Tangents, not sure if it can help in this situation but I wasn’t able to use it to solve this situation.

I know little maths and nothing about architecture, but all kind of help will be appreciate.

Thank you so much.

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#3

In theory, you would need one extra parameter ( diameter circle ) , for there are an infinite number of possibilities…!

Edit : Oops, did not see @DaveR already applied, btw: is there an ejercicio number

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Could Discourse show who is typing an answer to a specific topic?
#4

Hi Mike, thank you.

I was trying this exercise. I thought it wasn’t possible to deduct the diameter.
Any idea is welcome

EDIT: I don’t see that info on the blueprint.

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#5

Solved.

I didn’t pay attention well to the blue print.

And ecati told me how I can face the situation Can I draw an arc tangent to two circles?

TIG also said it was possible with his extension but I didn’t find the way with the extension, but I did with ecati method.

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#6

@MikeWayzovski, I didn’t understand your quote “btw: is there an ejercicio number”, are you asking me if it’s an exercise?

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#7

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#8

I quoted that site because my question had to do with the proposed exercise.
I’m still not sure if I understood what you meant.

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#9

You have quoted that site a few times, lately, and so I presumed that there was a relation to that site.

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#10

@MikeWayzovski I prefer you to make clear the question is on your mind and it will be a pleasure for me to answer it.

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#11

The red arc can be any radius greater than half of the sum of the distance between the centers of A and B, and Arad+ Brad
The minimum value is a circle which is tangential with A and B and is centered on a line drawn from A to B, offset appropriately.
The maximum radius [infinity] results in an arc than is effectively a straight line tangentially to A and B.
See the image for the need for an Xrad for an A & B tangential arc, and finding it’s center.

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#12

Awesome explanation TIG, I understood that I need to know the diameter or the center.
The radius is on the blueprint, but I didn’t realized at first.
Thank you.

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closed #13

This topic was automatically closed 91 days after the last reply. New replies are no longer allowed.

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