| 向量a |=1
(a-b)⊥(a+b)
(a-b)(a+b)=0
a^2=b^2=1
设b=(x,y)
(a-b)=(-1/2-x,√3/2-y)
(a+b)=(-1/2+x,√3/2+y)
(a-b)^2=(a+b)^2
4ab=0==>a⊥b
(-1/2,√3/2)(x,y)=0
-x+√3y=0
令x=√3,y=1
b ' =(√3,1)
|b'|=2
b=(±√3/2,±1/2)
(2)
ab=0
=90度；