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## Revit Trigonometry Problem

I am trying to solve the following problem. The goal is to create Parameters for the dimensions shown below with the arc always being tangent to the vertical reference plane and the angled line.

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## Re: Revit Trigonometry Problem

The key is to use the "Tangent End Arc" type and then constrain along [Edit:] both sides [End Edit] to set where the center of the arc is, not the radius. The radius will automatically adjust then. See the attached file below.

First, do a fillet arch so it gets positioned properly tangential to each sketch line. Then delete it and re-draw with the tangent end arc. I selected the bottom/angled line end and then the vertical line. Then I placed a dimension from the vertical end ref. plane to the center of the arc and parameterized it (radius). [Edit:] You need to add this same labeled dimension on the slanted line as well (radius) and now the arc stays tangential at all times [End Edit]. That does the trick and it should flex properly.

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## Re: Revit Trigonometry Problem

There's probably a comment somewhere in the Revit code that explains this functionality, but the comment never made it to the help file.

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## Re: Revit Trigonometry Problem

Unfortuntaly radiused support.rfa. does not solve the problem geometrically as the Radius is not Tangent to Angle. The links below may be reveal a solution to this problem. If so, the real issue here may be constraining the arc.

http://www.mathalino.com/reviewer/pl...area-trapezoid

http://www.mathalino.com/reviewer/di...ution-calculus

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## Re: Revit Trigonometry Problem

This is not a trigonometric problem (at least, it doesn't have to be). Any way I flex the family attached above, I always get tangent arcs at both the vertical and angled edges. Please attach an example of where that's not working as I don't see it.

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## Re: Revit Trigonometry Problem

See attachment above.

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## Re: Revit Trigonometry Problem

Yeah I see the problem, and don't really see an easy fix for it, other than doing a bunch of lengthy trig formulas in the family.

*edit* nevermind, doing it like Dave mentioned works. After using the fillet arc tool and setting a radius value, delete the arc and re-draw with the tangent arc tool, coming off of your angled sketch line. Then put your Radius parameter back on it, and it now appears to behave with any radius value.

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## Re: Revit Trigonometry Problem

That's what I'm saying, the family I uploaded works. Flex it at any angle, radius, etc. and it behaves properly.

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## Re: Revit Trigonometry Problem

Hi all,

I was searching for this same problem. I downloaded your family (radiused_support) and only changed the angle to 1.0 degree (did nothing else). The arc then is not tangent anymore to the angled line. So this family doesn't flex as you say?

Just like the images ThinkRevit (post 4) shows in the attached images. When you play with the parameters it may look like its working but when you zoom in, you clearly see it's not.

I think it may just be impossible?

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## Re: Revit Trigonometry Problem

I now have a rebar detail component that has an angle and the bend diameter (depending on the rebar diameter) is adjusting nicely and tangent with the angled and vertical line. All the other flexing seems to work perfectly also.

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