Default UI Menu: Constraints/Equal Radius

Ribbon UI Menu:

Makes the first selected circle/arc have the same radius as the second circle/arc.

1. Start with two circles/arcs. Activate the Equal Radius constraint and select the arc whose radius you want to change.

1. Select the arc whose radius you want to assign to the first arc.

The first arc's radius changes to match the second. The equal constraint (an equal sign) appears.

1. If you edit either arc, the equal radius constraint will be maintained.