Required Basic Knowledge.
Rhombus is a parallelogram with equal sides.
i.e.
diagonals bisect eachother. (DE=EB),(AE=EC) &(AED = DEC = CEB = BEA =90°)
And
AD=DC=CB=BA
SOLUTION
——————
Cosider ∆ADE;
AED =90° (refer above details)
given. DAE=30°
DE=6cm (DE=EB; also refer above)
To find:length of AD
Taking Cosine of Angle A
Cos(A) =DE/AD
->Cos(30°) =6cm/(AD)
->(√3/2) = 6cm/(AD)
-> AD =6÷(√3/2) cm
->AD =6×(2/√3) cm
->AD =12/√3 cm (;√3=1.73 .approximately)
->DA=12/1.73 cm
-> DA = 6.936 cm (approx.)
Hope it helps...
Regards,
Leukonov/Olegion.