It is given that m ∠ AOB = 42 ∘ and m ∠ EOF = 66 ∘ . By the , ∠ EOF ≅ ∠ BOC . Therefore, m ∠ BOC = 66 ∘ . By the , m ∠ AOC = 108 ∘ , and by the , m ∠ AOC + m ∠ COD = 180 ∘ . After application of the , m ∠ COD = 72 ∘ .