# Homework Help: Vectors: The Dot Product

1. May 1, 2007

### katrina007

Need help with this problem. I need to show that one side equals the other. I this is distributive property but isnt that just too plain simple? I mean im in pre-cal class and therefore this question cant be easy as it seems.... :

anyways, if anyone knows about vector plez help me with this.

Last edited by a moderator: Apr 22, 2017
2. May 1, 2007

### robphy

Realize that the plus-symbol on the left applies to adding vectors,
whereas the plus-symbol on the right applies to adding scalars.

What is your working definition of the dot-product?
ab cos(angle between)? or ax*bx+ay*by+az*bz? or something else?

3. May 1, 2007

### katrina007

Hi,

the teacher provide the following definition for the dot product:

The dot product of U = (U1, U2) and V = (V1, V2) is
U * V = U1V1 + U2V2

4. May 1, 2007

### Sojourner01

So, state the forms of each vector involved in terms of their components, then perform the scalar multiplications longhand. The definitions should drop right out.

5. Aug 4, 2007

### hamsawi

i have a text book that states; teh dot product of x1,x2 and y1,y2 is x1y1 - x2y1 -x1y2 + 4x2y2

how can that be? the it states the dot product of x1,x2 and x1,x2 is (x1-x2)^2 +3Xx^2 ? plz help