Question

What is the measure of DG?

Answer 1

Problem 1)

Minor arc DG is 110 degrees because we double the inscribed angle (DHG) to get 2*55 = 110


Answer: 110 degrees

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Problem 2)

Central angle GDC is the same measure as arc GFC. The central angle cuts off this arc.

The arcs GEC and GFC both combine to form a full circle. There are no gaps or overlapping portions.

So they must add to 360 degrees

(arc GEC) + (arc GFC) = 360
(230) + (arc GFC) = 360
(230) + (arc GFC)-230 = 360-230
arc GCF = 130 


Answer: 130 degrees

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Problem 3)

Similar to problem 1, we have another inscribed angle. ABC is the inscribed angle that cuts off minor arc AC

So by the inscribed angle theorem
arc AC = 2*(inscribed angle ABC)
3x+9 = 2*(3x-1.5)

Solve for x
3x+9 = 2*(3x-1.5)
3x+9 = 6x-3
9+3 = 6x-3x
12 = 3x
3x = 12
3x/3 = 12/3
x = 4

If x = 4, then 
arc AC = 3x+9
arc AC = 3*4+9
arc AC = 21


Answer: 21 degrees

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Problem 4)

Since we have congruent chords, this means that the subtended arcs are congruent. In this case, the arcs in question are CO and HZ

So arc CO is congruent to arc HZ


Answer is choice D

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Problem 5)

We have a right triangle due to Thale's theorem

The angles 75 degrees and x degrees are complementary angles. They must add to 90

x+75 = 90
x+75-75 = 90-75
x = 15


Answer: Choice D) 15