ABCD is a rhombus, then the measure of ∠ CDB is
30°
60°
55°
70°
We have ∠ A = ∠ C = 60° (opposite angle of parallelogram are equal)
Let, ∠ CDB = x
In triangle CDB we have
CD = BC (side of rhombus are equal)
So, ∠ CDB = ∠ DBC = x
therefore, ∠ CDB + ∠ DBC + 60° = 180°
2x = 120°
x = 60°
∠ CDB = 60°