Acute angle < 90°
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Answer:
There are 5 faces, 5 vertices, and 8 edges, so all of that together is 18
Lets assume center point of circle as O
OD is the radius of circle . so OD is also 7
All the sides of the triangle are equal . so angle at the center O is 60 degree.
radius = 7
Length of arc CD = 
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