Excuse me: vector multiplied by a non-zero vector equal to the zero vector?

Excuse me: vector multiplied by a non-zero vector equal to the zero vector?

High School: The product of a vector multiplied by a vector is a quantity product, so a zero vector multiplied by a non-zero vector equals zero!
In university: the product of a vector and a vector is divided into an inner product and an outer product. The inner product is the product of quantities, and the outer product is the zero vector multiplied by a non-zero vector.

Given vector a=(-1,2,3), vector b=(1,1,1), then the projective length of vector a on vector b is?

A.b=-1*1+1*2+1*3=4;
The projection of vector a on vector b = a.b/|b|=4/ root number 3;
The projective length of vector a on vector b =4/ root number 3;

Prove: vector AB•CD+BC•AD+CA•BD=0

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Let vector a and vector b be two non-collinear non-zero vectors (t∈R) (1) If vector OA=vector a, vector OB=tvector b, vector OC=1/3(vector a+vector b), then what is the value of real number t, A, B and C are collinear? (2) If vector a = vector b =1 and the angle between vector a and vector b is 120°, then what is the value of vector a-x vector b? There's only one answer.

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If a, b are two non-collinear nonzero vectors, t belongs to R. (1) If the starting points of a and b are the same, what is the value of t? (2) If |a|=|b| and the angle between a and b is 60°, what is the value of t? If a, b are two non-collinear nonzero vectors, t belongs to R. (1) If the starting points a and b are the same, what is the value of t, a, tb,(a+b)/3 The end point of the three vectors is on the straight line? (2) If |a|=|b| and the angle between a and b is 60°, what is the value of t?

Let vector OA=a, OB=tb, OC=1/3(a+b), if the terminal point of the three vectors is on a straight line, there must be a vector AC=mAB, where m is a real number, vector AC=OC-OA=(b-2a)/3, vector AB=tb-a, then there is (b-2a)/3=m (tb-a), and the corresponding coefficient is proportional.

What is the vector a multiplied by vector b? What is the vector a multiplied by the vector b?

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