In what ratio are the sides of a triangle if one of the angles is 120° and the sides of the triangle make up a arethmetic sequence..

so we have 3 sides:

a = a

b = a +d

c = a +2d

and one of the angles is 120° = angle between a and a+d (the shortest sides)..

i tried a lot of things but i couldnt find a way to get the right result. =(