Question

问下有夜猫子学霸么,|a|=3,|b|=4,|c|=5,a+b+c=0求||axb|+|bxc|+|cxa||=?

Answer 1

|a|=3,|b|=4,|c|=5,a+b+c=0

求|a×b+b×c+c×a|=_______

【解】c=-a-b

a×b+b×c+c×a

=a×b+b×(-a-b)+(-a-b)×a

=a×b+b×(-a)+(-b)×a

=3(a×b)

|a|=3,|b|=4,|c|=5,a+b+c=0

所以,a⊥b

|a×b+b×c+c×a|=3|a×b|=3|a| |b|=36