# Vectors

• September 2nd 2008, 02:37 PM
viet
Vectors
Quote:

Consider two vectors by A = 2 i - 2 j and B = - i - 6 j.
1) What is the direction of A + B? (from the +x axis)
I have A + B = 1 i - 8 j, and |A + B| = 8.06,
what i need to do to get the direction?
• September 2nd 2008, 02:40 PM
Chris L T521
Quote:

Originally Posted by viet
I have A + B = 1 i - 8 j, and |A + B| = 8.06,
what i need to do to get the direction?

The angle is determined by $\vartheta=\tan^{-1}\left(\frac{v_y}{v_x}\right)$, where $v_x~and~v_y$ are the components of a vector $\vec{v}$

So, in our case, $\vec{A}+\vec{B}$ (which I will denote as $\vec{V}$) is $\vec{i}-8\vec{j}$

Thus, $\vartheta=\tan^{-1}\left(\frac{-8}{1}\right)\approx\dots$

I hope this helps! (Sun)

--Chris
• September 2nd 2008, 02:51 PM
viet
easier than what i expected. tyvm Chris.