COA = COB
EOB = 56°
DOA = EOF
DOC = ?

Respuesta:
∡DOC = 22°
Explicación paso a paso:
∡EOB = ∡EOF = 56°
∡DOA = ∡EOF = 56°
∡AOB = 180 - (56 + 56) = 180 - 112 = 68
∡BOD = 68 - 56 = 12
∡COA = ∡COB = y
y + y + 56 + 56 = 180
2y + 112 = 180
2y = 68
y = 34
∡DOC = ∡COB - BOD
∡DOC = 34 - 12 = 22