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Tangents to a circle or arc

Posted: Tue Sep 02, 2014 1:13 am
by dhellew2
Sometime my brain works sometimes it's just really slow.. :?

Create the circle at the desired location
Draw two vectors from the center of the circle at the desired angle
Offset each vector the radius of the circle
Clip the unneeded part of the circle and you will have two vectors tangent to the circle
tangent 2.png
To create tangents to a center point arc draw temporary vector lines at 90° to the desired tangent lines
Create the center point arc
Draw vector lines snapped to arc ends at 90° to temporary vectors

Dale

Re: Tangents to a circle or arc

Posted: Tue Sep 02, 2014 1:53 am
by FixitMike
Much easier to download and install the Tangents gadget from here: http://gadgets.vectric.com/index.php?op ... Itemid=186

Re: Tangents to a circle or arc

Posted: Tue Sep 02, 2014 2:50 am
by mtylerfl
Great tip, Dale. Thank you!

Re: Tangents to a circle or arc

Posted: Wed Sep 03, 2014 1:31 am
by dhellew2
FixitMike, Thanks, but I already have the tangent gadget and have used it.

It doesn't work too well to create tangents at a specific angle.
It only creates tangent vectors between two circles which can be made to work if the angle of the tangent lines are not critical, or by doing some trig calculations to size the circles and the distance apart necessary to achieve the desired tangent lines at specific angles.,.

Michael T, hope you can use it.

Dale

Re: Tangents to a circle or arc

Posted: Wed Sep 03, 2014 1:56 am
by FixitMike
The offset function is quite useful for this and other constructions. I often use it to construct a fillet between two arcs. Offset both arcs by the radius of the desired fillet, and draw a circle with the desired fillet radius centered where the offsets intersect, and then trim away. Sometimes you have to draw lines between the centers of the fillet and the original circles first, as the trim tool doesn't always recognize tangent points as intersections.

Re: Tangents to a circle or arc

Posted: Thu Sep 04, 2014 11:26 pm
by dhellew2
Mike, Is this what you are creating? Dale
arc fillet.png

Re: Tangents to a circle or arc

Posted: Fri Sep 05, 2014 1:13 am
by FixitMike
Dale: No. Here's a picture of what I was describing.
Arc trim.JPG

Re: Tangents to a circle or arc

Posted: Wed Sep 10, 2014 6:15 pm
by dhellew2
Thanks Mike, now there are a couple new uses for offsets. Dale