If the straight sides of a triangular section of a lined canal with circular bottom of radius R, make an angle θ with horizontal, the perimeter of the canal is
A
R (θ + tan θ)
B
2R (θ + tan θ)
C
R (θ + cos θ)
D
2R (θ + cos θ)
Correct Answer: 2R (θ + cos θ)