B~a=a*b/a*a, it is known that the modulus of A is greater than that of B, and both a~b and B~a belong to a set (n/2èn is an integer, then b~a= 1/2.

B ~ a = [a] [b] cos @/[a] = 1/2 = [b] cos @/[a], cos @ less than1greater than 1/2, [b]/[a]

A~b=[a]cos@/[b]=2t*t, so a ~ b can only be 1 or 3/2. If a~b is 1, @=45 degrees, if a~b is 3/2, it is 30 degrees. The 45-degree return a~b does not match, so it is 3/2.