For a shoe brake, the equivalent coefficient of friction is equal to (where μ = Actual coefficient of friction, and θ = Semi-block angle)

A. 2μ sinθ/(θ + sinθ)

B. μ sinθ/(2θ + sin 2θ)

C. 4μ sinθ/(θ + sinθ)

D. 4μ sinθ/(2θ + sin 2θ)

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