If vec a vec b and vec c are non-zero vectors are such that vec a=2vec b ,vec b=vec c+vec d and vec d=vec a+vec c then the angle between vec a and vec d is?

If vec a vec b and vec c are non-zero vectors are such that vec a=2vec

1.	If vec a vec b and vec c are non-zero vectors are such that vec a=2vec b ,vec b=vec c+vec d and vec d=vec a+vec c then the angle between vec a and vec d is?
Answer» If vec a vec b and vec c are non-zero vectors are such that vec a=2vec b ,vec b=vec c+vec d and vec d=vec a+vec c then the angle between vec a and vec d is?