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Vector addition etc

  • Thread starter w0lfed
  • Start date
1. Homework Statement
Find the angle between the following vectors?
A = -2.00i^ + 6.00j^ and B = 2.00i^ - 3.00j^ (the ^ means 'i hat')



2. Homework Equations
Theta = tan^-1 = (opposite/adjacent)


3. The Attempt at a Solution
i said for the first part of the component that
theta(A) = tan^1 (6/2) = 71.57
and then did the same for the other component
theta(B) = tan^1 (2/3) = 33.70

and the angle between them should be the addition of those two? ie 105.27?
im confused...this doesnt look right
 
Have you done dot or cross products yet? If you have the easiest way to compute the angle is through the association that

[tex]\mathbf{A}\cdot\mathbf{B}=|\mathbf{A}||\mathbf{B}|\cos{\theta}[/tex]

or with cross products

[tex]|\mathbf{A}\times\mathbf{B}|=|\mathbf{A}||\mathbf{B}|\sin{\theta}[/tex]

where [itex]\theta[/itex] is the angle in between them.
 
nope, ive never seen that before?
 

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