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Answer :

Answer:

a=21

b=69

c=42

d=138

Step-by-step explanation:

c is supplementary to d (which is 138), so c=180-138= 42.

angle b is on the edge of the central angle 138, so b is 1/2, therefore, b=69.

angle a is complementary to angle b because any triangle that includes the diameter is a right angle, so angle a=90-69=21.

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