- #1

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vectors a - b + c = 0 ,determine the values of a dot b - adot c - b dot c if

|a|=1, |b|=2 and |c|=3

|a|=1, |b|=2 and |c|=3

- Thread starter bngo93
- Start date

- #1

- 4

- 0

vectors a - b + c = 0 ,determine the values of a dot b - adot c - b dot c if

|a|=1, |b|=2 and |c|=3

|a|=1, |b|=2 and |c|=3

- #2

- 164

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Let's say you have for example vectors w, x, y, if you have x*y + w*y, it is the same as y*(x+w), where * indicates dot product and x+w is the sum of both vectors.

- #3

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oh i have no idea how to start this problem my first attempt was horrible

i just changed the |a| to a*a by squaring both sides

i dont know if im on the right track but ill just try and see where it leads

It leads to a dead end : [

i just changed the |a| to a*a by squaring both sides

i dont know if im on the right track but ill just try and see where it leads

It leads to a dead end : [

Last edited:

- #4

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im lost ;/

- #5

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- #6

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umm would the values be the ones listed? with the magnitudes

and how did u get -a??

and how did u get -a??

- #7

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- #8

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Actually, a triangle is not quite the right word to describe

how the vectors a, -b, c relate to each other.

An improved question:

if we attempt to draw that triangle, what figure do we get?

Hopefully, the answer will be clear, once you have the correct figure. However, if necessary, apply law of cosines

Google can be a good refresher or

http://mathworld.wolfram.com/LawofCosines.html

Please let us know what figure you get, & if you still need help after drawing the figure.

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