Adjacent Arcs
Circles have infinitely many arcs, not just 3.
No
Diameter
Trefoil
Major arc is the longer of two arcs.
Yes, there can be congruent arcs on a circle. Arcs which subtend the same angle at the center are considered as congruent.
Congruent Arcs
Adjacent Arcs
Circles have infinitely many arcs, not just 3.
Half of the circle is an arc
No
Divide the arc's degree measure by 360°, then multiply by the circumference of the circle.
Because they are parts of the circumference of a circle
Diameter
In the same circle, or in congruent circles, two minor arcs are congruent if and only if their corresponding chords are congruent.
Trefoil