ABCD is a rhombus.
⇒BD = BC ........(1)(given)
BC = CD .....(2)(side of rhombus)
From equations (1) and (2)
BD = BC = CD
⇒△BCD is equilateral triangle. (1 mark)
So, ∠BCD = 60°
∠C = ∠A = 60° (Opposite angles)
∠ABC = ∠ADC = 180 – 60 = 120° (Adjacent angles are supplementary).
Angles of the rhombus are;
∠A = 60°, ∠ B = 120°, ∠C = 60°, and ∠D = 120° (1 mark)