Vector Components and Dot Product Proof

In summary: So \hat x \cdot \vec A = a. What about the others?In summary, to show that a1 = x hat (dot) A, a2 = y hat (dot) A, and a3 = z hat (dot)A, one must first understand that the hats represent unit vectors in the x, y, and z directions and that A represents a vector with components a, b, and c. Then, by taking the dot product of both sides of the equation with each of the basis vectors (x hat, y hat, and z hat), one can show that a1 = x hat (dot) A, a2 = y hat (dot) A, and a3 = z hat
  • #1
bossman007
60
0

Homework Statement



A is a vector

Show that: a1 = x hat (dot) A
a2 = y hat (dot) A
a3 = z hat (dot)A

Homework Equations



A= (a1*x hat) + a2*y hat) + (a3* z hat)

The Attempt at a Solution



my hint says to take the dot product of both sides of the equation in (2) with each of the basis vectors in turn.

Doing this I get A^2 = [(a1*x hat) + a2*y hat) + (a3* z hat)] dot A

I don't know what to do next, or if that's even right.
 
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  • #2
bossman007 said:

Homework Statement



A is a vector

Show that: a1 = x hat (dot) A
a2 = y hat (dot) A
a3 = z hat (dot)A
You haven't told us what a1, a2, and a3 are, nor have you said what "x hat" and the other two hats represent.

Don't make us try to read your mind...
bossman007 said:

Homework Equations



A= (a1*x hat) + a2*y hat) + (a3* z hat)
Is this given? If so, you need to say so.
bossman007 said:

The Attempt at a Solution



my hint says to take the dot product of both sides of the equation in (2) with each of the basis vectors in turn.

Doing this I get A^2 = [(a1*x hat) + a2*y hat) + (a3* z hat)] dot A

I don't know what to do next, or if that's even right.


A2 has no meaning - you can't just multiply a vector by itself. You can dot it with itself, but you don't get A2.
 
  • #3
Are ##\hat x, \hat y, \hat z## the unit vectors in the x,y, and z directions, more commonly known as i, j, and k? And is ##\vec A = a\mathbf{i} +b\mathbf{j} + c\mathbf{k}##? If so, the problem is pretty easy. Remember the basis vectors are perpendicular. What happens if you dot i into both sides?
 
  • #4
I tried what I thought you meant to try, here's what I did. I dotted both sides of the equation by x-hat in my case instead of ur i-hat example. Here's what I got. Dunno if on right track or not.

[PLAIN]http://postimage.org/image/6zbkosjsp/ [/PLAIN]
 
Last edited by a moderator:
  • #5
What do you think [itex]\hat x \cdot \hat x[/itex] is?
 
  • #6
x hat dot x hat = x^2
 
  • #7
Mm, nope. What is the significance of the hat? What does a hat tell us about a vector?
 
  • #8
that it's a unit vector , which equals one?

so x-hat (dot) x-hat = 1?
 
  • #9
That it's a unit vector, so its length is 1. Dot product of a vector with itself gives the length squared, but [itex]1^2 = 1[/itex], so yeah.
 

Related to Vector Components and Dot Product Proof

1. What are vector components?

Vector components are the individual parts that make up a vector. They are typically represented by the x and y axes in a two-dimensional coordinate system, or by the x, y, and z axes in a three-dimensional coordinate system.

2. How do you find the magnitude of a vector using its components?

The magnitude of a vector can be found using the Pythagorean theorem, where the magnitude is equal to the square root of the sum of the squares of the vector's components.

3. What is the formula for calculating the direction of a vector using its components?

The direction of a vector is typically represented by an angle, which can be calculated using the inverse tangent function. The formula is tan-1 (opposite/adjacent), where "opposite" is the y component and "adjacent" is the x component.

4. How do you prove that two vectors are orthogonal using their components?

To prove that two vectors are orthogonal (perpendicular), you can use the dot product method. If the dot product of two vectors is equal to 0, then they are orthogonal. The dot product is calculated by multiplying the corresponding components of the vectors and then adding them together.

5. Can vector components be negative?

Yes, vector components can be negative. This typically occurs when the vector is pointing in the direction opposite to the positive axis. It is important to pay attention to the signs of vector components when performing calculations involving vectors.

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