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I want to create a bunch of arcs by creating circles and then dividing those circles' perimeters into arcs by intersecting them with another shape.

However when I do this I end up with a shape not a path. How could I go about dividing circles by another shape so that I'm only left with paths, not shapes with internal area?

Eg this is what I am left with after dividing a circle with another shape:

enter image description here

Whereas I just wanted to be left with the outside path as an arc, not the moon-like shape that I currently have.

PS I'm very new to Illustrator so please go easy on me :)

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    Can't you just delete the anchor points you don't want after the operation? Or did I understand it wrong? – Luciano Jan 27 '17 at 11:03
  • Yes, that does seem to do the trick! That involves a few extra steps though, especially with complex shapes where you can be left with a bunch of weird small lines. Is there a way to just divide objects into lines (ie not paths) from the start? – Aron Jan 27 '17 at 11:06
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Try this method if it can satisfy your requirements :-)

Using Eclipse tool you can create perfect circle shape by pressing Command+Shift while dragging the mouse for its width and height or you can input in transform window in exact diameter you want.enter image description here

Copy the first circle path then Paste it in back (Ctrl+C then Ctrl+B) Note: I use yellow (first) and cyan(second) to differentiate each other. It is useful to see where is you path in Layer Panel which is on top of each other. enter image description here

Use the scale tool to make the cyan path bigger. Press the Alt key then point to the right point of the circle. This is to control where the scaled circle which is the cyan starts from. Normally the anchor point starts from the center so we need to change it to achieve the desired shape. You notice the anchorpoint changes and a pop up menu will appear. enter image description here

Change the value to the desired thickness of the crescent you want to do. enter image description here enter image description here

Now with both cyan and yellow selected. Open the Pathfinder window. You can see there MinusFront (refer to the illustration). Pathfinder > Shapemodes > MinusFront

enter image description here

last for the arcs (i mis-interpreted it that you like the moon)

you have many techniques to use but it boils down to Scissor Tool or Cutter. Here are samples how to cut. Option A is cut with line and divide (pathfinder window). The step will be 2 circle paths + Draw 1 line to the right then click divide. delete the excess / residual path then Scissor Tool. Option B Direct Scissor tool then delete un-wanted areas. enter image description here enter image description here

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I know that this is an old topic and the previous answers have been educational and revealing to me; I'm fairly new to Illustrator. I discovered this thread in my search for the same thing the OP sought; a way to divide a circular path into precise arcs by superimposing another shape. I couldn't find an answer that satisfied my needs but, luckily, I eventually figured it out. Here's how:

1) Create a circle with a diameter equal to the radius of the desired arc. Give it a stroke but no fill. Turn on Smart Guides. This next part will be a bit tricky, if you haven't done this before, so read this next step before attempting it.

2) Select the Polar Grid tool from within the Line Tools palette. Position the cursor over the center of the circle (that's why you have Smart Guides on) and Alt-Shift-drag (or Option-Shift-drag) out from the center until the polar grid's outer circle is larger than your original circle. Holding down the Alt-Shift (or Option-Shift) keys will constrain the polar grid to the center of your original circle and keep it perfectly round. DO NOT let go of the mouse button. (In the image below, I have let go of the Option-Shift)

Creating Polar Grid (not constrained)

You'll note that the polar grid contains a number of concentric circles and a number of radial dividers. Keep your mouse button down with your mousing hand but let go of the Alt-Shift (or Option-Shift) keys with the other; the polar grid will move but do not let this throw you and do not stop pressing the mouse button. Now, using your non-mouse hand, press the down-arrow key until there are no concentric rings inside the polar grid's outer circle. Then use the same hand to press the right-arrow or left-arrow keys to increase or decrease the number of dividers to create the number of divisions you want. If you want a 22.5˚ arc, for example, divide 360˚ ÷ 22.5˚ to get 16, the number of radial dividing lines you'll need. You are still holding down the mouse button, right?

Polar grid with concentric circles cleared and desired divisions

Once you've cleared the concentric circles away and arrived at the number of divisions you need, press the Alt-Shift (Option-Shift) keys again. When you do, the polar grid will now pop back to the center of the original circle and will be constrained to perfectly round. Now let go of the mouse button to create the polar grid. You should now have your original circle overlaid by a polar grid consisting of the number of dividers you need and one outer circle.

Polar grid overlaying original circle

The polar grid is actually a group consisting of to groups; the outer circle and the group of radial lines that constitute our dividers. Using the Layers Panel, twirl open the polar grid group, select the outer circle and drag it to the trash bin in the Layers Panel to delete it. Leave the radial dividers grouped.

Polar grid's outer circle removed, leaving grouped dividers overlaying circle

3) Now select both the original circle and the group of radial lines and use the Pathfinder to cut the original circle into segments. There are two ways you can do this: A) Use the 'Outline' tool, which will cut all the lines and arcs into discrete path segments OR B) Use the 'Divide' tool to cut the original circle into pie-shaped objects (in this case, you will need to select the point of the pie-shaped object with the Direct Selection tool (white arrow) and delete it to create the arc-shaped path)

Using the 'Outline' tool

Using the 'Divide' tool

Whichever tool you use, you'll need to 'Ungroup' the resulting paths (or shapes, in the case of the 'Divide' tool) in order to select and move them and create the objects you desire. If you use the 'Outline' tool, it will remove the stroke, so you'll have to apply a new one in order to see the path segments. The 'Divide' tool will leave the stroke intact but, again, you'll need to select and delete the center point of each segment in order to reduce the shape to the path you desire.

After using 'Outline' and applying a stroke

After using 'Divide'

I hope that this will prove useful to others. Best Wishes to All and, as Elrond would say "Nasië i eleni síluva tielyanna!" ("May the Stars Shine Upon Your Path!")

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To create arc you can use Arc Tool https://helpx.adobe.com/illustrator/using/drawing-simple-lines-shapes.html or use Scissors tool https://helpx.adobe.com/illustrator/using/cutting-dividing-objects.html to divide circle in any places.

  • 1) that link is dead, 2) the arc tool only draws quarter circles, 3) I want to cut the circle specifically where it intersects with another shape – Aron Jan 27 '17 at 13:55
  • In this case you can use: select all shapes then Pathfinder->Outline, then ungroup, apply any stroke width, it will divide shapes into pathes. – emax Jan 27 '17 at 14:29
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Make your overlapping circles with fill and no stroke.

Select them all, try "trim" or "intersect" from the pathfinder palette, although I think you can do it with "divide".

Ungroup them, delete the parts you don't want, switch fill to stroke.

Drag over the inner line of the moon with the white arrow tool and hit delete. This should leave you with only the outer arc path.

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