The combination coefficient of linear representation of ai is the component of ai.
So there is (a 1, a2, a3)=(e 1, e2, e3) a.
For example, in R 2, A 1 = (1, 24) t and A2 = (3 3,4) t.
Then a 1 = e 1+2e2, a2 = 3e 1+4e2.
So (a 1, a2) = (e 1, e2) *
1 3
2 4
= (e 1,e2)A