Answer: 108 degrees
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Step-by-step explanation:
Angle ABC is given to be 90 degrees. By the converse of Thales Theorem, we know that AC is a diameter of the circle.
If we draw a line from A to C, it will pass through the center of the circle.
Therefore, arc AC is 180 degrees as this is half the distance around the circle.
minor arc AD = 72
minor arc CD = x
(minor arc AD) + (minor arc CD) = arc AC
72+x = 180
72+x-72 = 180-72
x = 108
minor arc CD is 108 degrees