Here is an easier way to create an arc radius from an outside point tangent to another arc.
1. Create a circle that is 3" larger than the small arc centered on the small arc (let's say the small arc is .5" then you would create a 3.5" radius circle).
2. Create a 3" radius circle centered on the point.
3. You will get two intersections. Pick the intersection on the side
you want the tangent to be on and create a 3" radius circle.
4. Split the last 3" circle, trim it to the point and small arc, and delete the first two circles.
This method also works to create an arc tangent to two other arcs.
I started to put this in the hints and tips forum but then I found this thread.
1. Create a circle that is 3" larger than the small arc centered on the small arc (let's say the small arc is .5" then you would create a 3.5" radius circle).
2. Create a 3" radius circle centered on the point.
3. You will get two intersections. Pick the intersection on the side
you want the tangent to be on and create a 3" radius circle.
4. Split the last 3" circle, trim it to the point and small arc, and delete the first two circles.
This method also works to create an arc tangent to two other arcs.
I started to put this in the hints and tips forum but then I found this thread.