Answer: Choice A) 148 degrees
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Explanation:
Let point A be the center of the circle.
Arc DCF is 316 degrees. Arc FG is 20 degrees. Subtracting the arc measures gives 316-20 = 296 which is the measure of arc DCG, and by extension, it is the measure of reflex angle DAG. The acute angle DAG is 360-296 = 64 degrees
Triangle DAG is isosceles with AD = AG, so the base angles are ADG and AGD. Let's call each of these angles x for now. The sum of the three angles add to 180
x+x+64 = 180
2x+64 = 180
2x = 180-64
2x = 116
x = 116/2
x = 58
Therefore angle ADG is 58 degrees. It adds to angle ADB = 90 to get 90+58 = 148, which is the measure of angle BDG.
Note: angle ADB is 90 because tangent BD forms a right angle with the radius AD.
Another note: angle ADG is half that of the arc it cuts off, so in a sense it's similar to an inscribed angle
