Question

The angle between a bar and b bar is pi/3,then find the angle between 2a bar and -3b bar?

Answer 1

Not certain what you mean by "a bar," but suspect its "the vector a." Best to explain your abbreviations, as not everyone would recognize "a bar" or "b bar."

Answer 2

I strongly suggest that you draw diagrams to show vectors A and B and the pi/3 angle between them, and 2A - 3B. Perhaps then it'll become clearer how to find the angle between 2A and -3B.

Answer 3

Thanks @mathmale but can I get the answer?

Answer 4

I always try to engage others in learning, rather than hand out answers, so must regretfully decline. If you'd care to draw these two vector situations, then we'd have something concrete to discuss.