# Vectors dot prodoct question/clarification

• May 22nd 2011, 10:38 AM
IanCarney
Vectors dot prodoct question/clarification
In the following question, would the answer be 22.5 or -22.5?

http://imageshack.us/m/862/1426/vectors.png

The answer in the back of the book says 22.5 so I'm not sure if I'm missing something or if it's a typo.
• May 22nd 2011, 10:47 AM
Plato
$\displaystyle \vec{a}\cdot\vec{b}=\|\vec{a}\|\|\vec{b}\|\cos(\al pha)$
• May 22nd 2011, 10:49 AM
TheEmptySet
Quote:

Originally Posted by IanCarney
In the following question, would the answer be 22.5 or -22.5?

http://imageshack.us/m/862/1426/vectors.png

The answer in the back of the book says 22.5 so I'm not sure if I'm missing something or if it's a typo.

The answer is correct. Notice that the vectors are not lined up tail to tail. What did you try and what did you get.
• May 22nd 2011, 11:05 AM
IanCarney
Quote:

Originally Posted by TheEmptySet
The answer is correct. Notice that the vectors are not lined up tail to tail. What did you try and what did you get.

Ah, I see. Thanks, I get it now.