How to draw a precise circular arc in Adobe Illustrator?

Question

Say, an arc with radius r centered at o, from angle a to angle b.

I don't see how to use Arc tool in Adobe Illustrator this way. What's the best way to draw it?

Answer 1

AI sucks for this. Illustrator doesn't draw "real" circles (ie., using centerpoint and radius) either, it makes an Ellipse using bezier curves.

Your best bet is to make a Ellipse with equal width & height (ie., a circle) and use 2 Line Segment shapes to intersect the Ellipse. It takes 3-4 steps instead of 1, but it will allow you to use specific dimensions.

Answer 2

Use the pie graph tool! It's a bit of a hack but it works.

Example: Creating a 30° angle.

1. Create a pie graph with the dimensions you want.
2. Calculate the angle in terms of revolutions of a full circle. 30°/360° = 1/12 revolutions.
3. Create a pie graph with the values 1 and 11 (1/12 + 11/12 = 1 or 100%)
4. Ungroup the graph object and select the wedge that corresponds the angle.

Answer 3

Farray's answer is the standard way. Another way is to use scripting. One script that could help is the "Circle" script from here http://park12.wakwak.com/~shp/lc/et/en_aics_script.html. It will create a circle with a given number of equal segments, want a 60° arc, make six segment circle and delete all but one segment. Another option (if you have some programming skills) could be to creating your own script. Scriptographer is a scripting plugin for Illustrator that adds some constructors to allow you to create arcs in your own scripts.

Answer 4

Unless things were improved, you have to still draw a symmetrical ellipse (circle) then use the "c" (scissors) to to cut it to size. The "scientific" way takes about as many steps and is less visual. A black hat is a hat black (French proverb.) It would be nice if you could specify and angle and radius then move the results into position.