GRE
a
b
The perimeter of the regular polygon
3 times the perimeter of triangle OAB
Length of AC
Length of BE
∠ABD
∠BCD + ∠CDB
Length of AB
Length of BC
AB
BC
The perimeter of the triangle
15
∠B
∠C
The perimeter of rectangular
The sum of the perimeter of two triangles
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