Question

已知非零向量a,b,若a·b=0,则|a-2b|/|a+2b|等于?

Answer 1

根号(|a-2b|)^2/根号(|a+2b|)^2=根号[(a^2-4a·b+4b^2)/(a^2+4a·b+4b^2)]=根号[(a^2+4b^2)/(a^2+4b^2)]=1 因为a·b=0,4a·b=0