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## #1 2013-05-06 11:25:13

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Scalar product problem

The problem with me is that I don't know how I will replace the vectors by which values?
The problem is attached in as an image.

Last edited by Omareg94 (2013-05-06 11:26:49)

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## #2 2013-05-06 11:26:08

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

Hi Omareg94;

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #3 2013-05-06 11:28:29

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

Post updated.  Please enable me to include links in my posts to be able to add images quickly..  Thanks!

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## #4 2013-05-06 11:34:57

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

Hi Omareg94;

I am unable to do that. The rule about no links until you are a member and have been here a while is a forum rule. You will have to provide a link to the image as you have done in post #1.

What is the circle with a dot inside mean?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #5 2013-05-06 11:36:27

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

Ok.  No problem!

The circle with a dot inside means; scalar product

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## #6 2013-05-06 11:44:20

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

Hi;

Oh okay, you mean the dot product

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #7 2013-05-06 11:48:28

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

Yes, i mean the dot product

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## #8 2013-05-06 13:09:47

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

Any more drawings that you need to upload?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #9 2013-05-06 13:17:25

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

I solved it that way but I am not sure if I have did something wrong

Last edited by Omareg94 (2013-05-06 13:17:48)

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## #10 2013-05-06 13:36:44

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

Hi;

That drawing is not coming in very well for me. What did you get for 1?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #11 2013-05-06 13:42:43

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

100 from a.b=abcosθ
I suggested that a=10 as the side length of the square equal 10cm, is that ok?

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## #12 2013-05-06 13:48:29

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

I did it another way and got 100.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #13 2013-05-06 14:12:51

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

I think both are ok but I need someone to confirm my answer.. Let's wait

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## #14 2013-05-06 14:15:08

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Scalar product problem

The magnitudes are 10 so the formula is just plug in but yes wait for the vector people to show up.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #15 2013-05-07 07:04:22

bob bundy
Registered: 2010-06-20
Posts: 8,322

### Re: Scalar product problem

Hi Omar,

I've been out all day in the big city.  Just got back.

1, 2, 3 and 6 look ok to me.

4 and 5 ?  Two ways to do these:

(i) Magnitude of vector 1 x magnitude of vector 2 x cosine of angle between.  You don't appear to have the right magnitudes for the diagonals.

(ii) Split the diagonals into two components, and do the scalar product of each, adding the results together.  Same answer either way.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #16 2013-05-07 07:09:16

Omareg94
Member
Registered: 2013-04-26
Posts: 13

### Re: Scalar product problem

Oh yes,, I see that magnitudes of diagonals in 4 and 5 are wrong it must be 10√2 not 10
Thanld a lot!

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## #17 2013-05-07 08:34:19

bob bundy
Registered: 2010-06-20
Posts: 8,322

### Re: Scalar product problem

Correct.

If you want to post new answers, I'll check them for you.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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