Let the acute angle be A and obtuse angle be B.

Rhombus ABCD, and angle A = angle C = acute angles.

The perpendicular from B to AD be BE.

Now in ÎABE, AE = ED = AB/2 = AD/2

cos A = AE/AB = 1/2

angle A = 60^{0} = angle C

angle B = angle D = (360 - 2x60)/2 = 120^{0}.