已知向量a=(sinx,1),b=(cosx,-1/2)

1.a⊥b时,a,b构成直角三角形,|a+b|^2=|a|^2+|b|^2=(sinx^2+1)+(cosx^2+1/4)=9/4=>|a+b|=3/22.f(x)=a(a-b)=a^2-a.b=sinx^2+1-(sinxcosx-1/2)=(1-cos2x)/2-sin2x/2+3/2=2-(sin2x+cos2x)/2=2-√2/2sin(2x+π/4)∈[2-√2...