# evaluate given vectors

• Dec 17th 2012, 12:18 PM
Itel
evaluate given vectors
Please can someone help with this? I've been having a lot of problems with this. And if you could explain it an not just give me the answer, I'm trying to actually learn how to do this. Thank you for any help you can provide.

Evaluate the expression:

v ⋅ w

Given the vectors:

r = <8, 8, -6>; v = <3, -8, -3>; w = <-4, -2, -6>
• Dec 17th 2012, 12:23 PM
Plato
Re: evaluate given vectors
Quote:

Originally Posted by Itel
Please can someone help with this? I've been having a lot of problems with this. And if you could explain it an not just give me the answer, I'm trying to actually learn how to do this. Thank you for any help you can provide.
Evaluate the expression:
v ⋅ w
Given the vectors:
r = <8, 8, -6>; v = <3, -8, -3>; w = <-4, -2, -6>

$\displaystyle <a,b,c>\cdot<x,y,z>=ax+by+cz$.
• Dec 17th 2012, 02:02 PM
Itel
Re: evaluate given vectors
Would it be
8*3
8*-8
-6*-3?
• Dec 17th 2012, 02:04 PM
Plato
Re: evaluate given vectors
Quote:

Originally Posted by Itel
Would it be
8*3
8*-8
-6*-3?

NO INDEED.

Apply the rule that I posted.
• Dec 17th 2012, 02:06 PM
Itel
Re: evaluate given vectors
Which is 24+-64+18=-22?
• Dec 17th 2012, 02:30 PM
Plato
Re: evaluate given vectors
Quote:

Originally Posted by Itel
Which is 24+-64+18=-22?

Which is correct. The dot product gives a number.
Because it is negative tells us that the angle between the vectors is obtuse.
• Dec 17th 2012, 03:15 PM
Itel
Re: evaluate given vectors
So that's the answer? -22 and its obtuse?
• Dec 17th 2012, 03:22 PM
skeeter
Re: evaluate given vectors
are you taking an online course?
• Dec 17th 2012, 03:37 PM
Itel
Re: evaluate given vectors
No. I'm in college.
• Dec 17th 2012, 03:45 PM
Plato
Re: evaluate given vectors
Quote:

Originally Posted by Itel
No. I'm in college.

REALLY? What in the world is that college is using as a textbook?
Please name both college and textbook, as well as the course name.

I find all your posts unbelievable coming from a college student studying anything to do with vectors.
• Dec 17th 2012, 03:51 PM
skeeter
Re: evaluate given vectors
Quote:

Evaluate the expression:

v ⋅ w

Given the vectors:

r = <8, 8, -6>; v = <3, -8, -3>; w = <-4, -2, -6>
$\displaystyle {\color{red}v \cdot w} = (3)(-4) + (-8)(-2) + (-3)(-6) = -12 + 16 + 18 = 22$

vector r = <8,8,-6> has no affect on the dot product of vectors v and w
• Dec 17th 2012, 03:54 PM
Itel
Re: evaluate given vectors
What you don't believe me? :P

West Georgia Technical College
Math 1131 (which is calculus)
ISBN 978-1-133-22867-7 or 1-133-22867-4 (I don't which one is which)