Question

If the angle A of a rhombus ABCD is 120 degree,prove that the triangle is equilateral.

Answer 1

join both the diagnol
now in the small ∆ABO. o being the intersection point of diagonal

now, angle OAB = half of angle A=60°

similarly, angle OBA=60°

with ASP

angle O=60°

hence ∆ is equilateral