Proof of Vector Equivalence: a‧b=a‧c

In summary, the conversation discusses the question of whether for any vectors a, b, c such that a is not equal to 0 and a‧b = a‧c, then b = c. The conversation goes on to explore potential solutions, such as finding a counterexample, and concludes that a specific example of a = (1, 0, 0), b = (1, 0, 1), c = (1, 2, 1) disproves the initial statement. It is also mentioned that the choice of vector space and dot product does not affect the validity of the counterexample.
  • #1
SOHAWONG
16
0
1.Determine if it is true that for any vectors a, b, c such that
a is not equal to 0 and a‧b = a‧ c, then b = c.



i tried to let a‧b-a‧c=0
then a‧(b-c)=0
but i found it's not meaningful
so how can i solve it =[
thz
 
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  • #2
Try to think of an example where it's not true.
 
  • #3
radou said:
Try to think of an example where it's not true.
the method i have tried is really useless?
 
  • #4
It's not useless, it just doesn't tell you anything.

You can solve this by finding a counterexample.
 
  • #5
radou said:
It's not useless, it just doesn't tell you anything.

You can solve this by finding a counterexample.
assume b is not equal to c
l.h.s=a‧b
=...
should i express the dot product?
 
  • #6
let a = (1, 0, 0), b = (1, 0, 1), c = (1, 2, 1).

What does a.(b - c) equal?
 
  • #7
radou said:
let a = (1, 0, 0), b = (1, 0, 1), c = (1, 2, 1).

What does a.(b - c) equal?
zero =[
btw,when we want some example for conradiction,we should use some real number to think about it first?
 
  • #8
It doesn't matter what you use.

If you're not talking about a specific set of vectors and a specific dot product, and if you assume that, for any non-zero a, and any b, c, the implication a.(b - c) = 0 ==> b = c holds (which is equivalent to a.b = a.c ==> b = c) then it doesn't matter which vector space and dot product you chose to construct your counterexample.

So, we found an example where a.(b - c) = 0, when b doesn't equal c.
 
  • #9
radou said:
It doesn't matter what you use.

If you're not talking about a specific set of vectors and a specific dot product, and if you assume that, for any non-zero a, and any b, c, the implication a.(b - c) = 0 ==> b = c holds (which is equivalent to a.b = a.c ==> b = c) then it doesn't matter which vector space and dot product you chose to construct your counterexample.

So, we found an example where a.(b - c) = 0, when b doesn't equal c.
a.(b - c) = 0, when b doesn't equal c
this i'd thought once,but don't know how to express
anyway thank you very much :p
 

1. What is vector equivalence?

Vector equivalence refers to the condition where two vectors have the same magnitude and direction.

2. How is vector equivalence proven?

Vector equivalence can be proven by showing that the dot product (a‧b) and (a‧c) of the two vectors are equal. This means that the angles between the two vectors are the same, and therefore they have the same direction.

3. What is the significance of vector equivalence?

Vector equivalence is important in mathematics and physics as it allows us to simplify and solve problems involving vectors. It also helps us understand the relationship between different vectors.

4. Can vector equivalence be applied to all types of vectors?

Yes, vector equivalence can be applied to all types of vectors, including 2D and 3D vectors, as long as they have the same magnitude and direction.

5. How does vector equivalence relate to vector addition and subtraction?

Vector equivalence is closely related to vector addition and subtraction. If two vectors are equivalent, then they can be added or subtracted to create a new vector with the same magnitude and direction.

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