Since It is a question of class XII , but i am providing you the the similar link so that you can get the idea.
https://www.meritnation.com/ask-answer/question/in-a-regular-hexagon-abcdef-ab-vector-a-and-bc-vector-b/vector-algebra/7539207
Regards
https://www.meritnation.com/ask-answer/question/in-a-regular-hexagon-abcdef-ab-vector-a-and-bc-vector-b/vector-algebra/7539207
Regards