(a-b)(a+b)
=a²-b²
=|a|²-|b|²=1,于是|b|=√2/2,于是|a||b|=√2/2
cosθ=ab/(|a||b|)=(1/2)/(√2/2)=√2/2,得θ=π/4
………………
|a+b|²
=(a+b)²
=a²+2ab+b²
=|a|²+2ab+|b|²
=1+1+(1/2)
=5/2
于是|a+b|=(√10)/2
(a-b)(a+b)
=a²-b²
=|a|²-|b|²=1,于是|b|=√2/2,于是|a||b|=√2/2
cosθ=ab/(|a||b|)=(1/2)/(√2/2)=√2/2,得θ=π/4
………………
|a+b|²
=(a+b)²
=a²+2ab+b²
=|a|²+2ab+|b|²
=1+1+(1/2)
=5/2
于是|a+b|=(√10)/2