In a rhombus ABCD,
∠ABC = 56°
So, ∠BCD = 2 (∠ACD) (Diagonals of a rhombus bisect the interior angles)
or ∠ACD = 1/2 (∠BCD) …..(1)
We know, consecutive angles of a rhombus are supplementary.
∠BCD + ∠ABC = 180°
∠BCD = 180° – 56° = 124°
Equation (1) ⇒ ∠ACD = 1/2 x 124° = 62°