## godorovg Group Title anyone feeling lucky tonight? I need another way to understand dot product rule in vectors? 2 years ago 2 years ago

1. Kainui

Well in what way do you understand the dot product rule as it stands? lol

2. godorovg

that is what I am asking to see if I get a better grip on this from what a with roof plus b with roof = c roof that is what the dot rule is right??

3. godorovg

I can not draw on this board I am really bad at it..

4. Kainui

|dw:1345012754225:dw| That? That doesn't look like a product to me, looks like a sum.

5. godorovg

okay, than I have this mixed up help me to get this straight plz

6. borcarlo

|dw:1345012796701:dw|

7. borcarlo

8. godorovg

the sum rule is what I posted the first time, why is this called the dot rule?"

9. godorovg

I know using this the dot you dots, but why? dots mostly means times in math.

10. borcarlo

Ok, so be clearer with your question.

11. Kainui

The dot product is $A*B=ABcos \theta$ while the cross product is $AxB=ABsin \theta$

12. godorovg

sorry I am trying too, here this is still new to me bare with me. Sorry if I have caused problems here or anything.

13. borcarlo

No but the thing is we don't to understand your question, actually I don't.

14. borcarlo

seem*

15. godorovg

I am trying to put this in words, I am not not using the right words here. The dot product is A∗B=ABcosθ this is what I am asking for and why and help me to understand the concept here

16. borcarlo

Imagine you have a vector say (1, 2)=a right, the length 2 is the portion of (1,2) on the y axis. There I took the dot product a°y^= (0,2) . So the dot product allows you make that same thing with any vector.

17. Kainui

I learned it in terms of flux. How many field lines are going through an area, for instance. So let's look at the two extremes. Remember that an area's vector is pointing out, perpendicular to the length and width of it. |dw:1345014748903:dw| So here we see on the left that the cosine of the angle between the two is 0, and the cosine of 0 is 1. So we have 100% flux through the area of electric field lines. Now in the right side we see that the electric field lines are going perpendicular to the area, so none of the field lines are traveling through the area. Cosine of 90 degrees is indeed 0, so we see there is no flux.

18. godorovg

thanks