Our teacher wrote the answer on the blackboard: root number 3. The steps are as follows: Because1| ba |? Vector ba = vector BA/|BA|, known vector ab = vector DC = [1, 1]. Make a parallelogram ABCD and connect BD. It is easy to know that AB = root number 2, because vector BA/ absolute value BA+ vector BC/ absolute value BC = root number 3 vector BD/ absolute value BD, so AB = BC = root number 2, because BD is connected. From the above, we can know that angle DAB = 120 degrees, angle ABC=60 degrees, S.

Hehe, it's a little rough. This is all my memory. Because you and I are both netizens, let me answer it for you.