In the given figure, equilateral △ABC is inscribed in a circle and ABCD is a quadrilateral, as shown. Then ∠BDC = ?
(a) 90∘
(b) 60∘
(c) 120∘
(d) 150∘
In the figure, ABCD is a cyclic quadrilateral in which AC and BD are its diagonals. If ∠DBC=55∘ and ∠BAC=45∘, find ∠BCD.