|a－b|²=1 ===>>> |a|²－2a*b＋|b|²=1 ===>>> 2|b|²－2a*b=1 ==>>>2b*b－2a*b=1 ==>>b*(a－b)=1/2|b－c|²=1/16 ==>> |b|²－2b*c＋|c|²=1/16 ==>>> |b|²－2b*c＋|b|²=1...