SOLUTION: How to prove that a*b=|a||b|, if a and b are two vectors in the same direction. Thank you.

Algebra ->  Matrices-and-determiminant -> SOLUTION: How to prove that a*b=|a||b|, if a and b are two vectors in the same direction. Thank you.       Log On


   

Question 1114600: How to prove that a*b=|a||b|, if a and b are two vectors in the same direction.
Thank you.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
By definition,
a%2Ab=abs%28a%29%2Aabs%28b%29%2Acos%28theta%29
Substituting,
abs%28a%29%2Aabs%28b%29=abs%28a%29%2Aabs%28b%29%2Acos%28theta%29
cos%28theta%29=1
theta=0
So angle between the two vectors is zero and they are pointed in the same direction.