# Vectors

• Feb 11th 2011, 05:26 PM
ziane0210
Vectors
Can anyone help me with this problem:
http://img819.imageshack.us/img819/2552/imgpv.jpg
• Feb 11th 2011, 05:28 PM
Ackbeet
This is more of a pre-calc or algebra question, just fyi. You can report your own post (use the little triangle symbol with the exclamation mark in it), and a mod will move it for you.

What ideas have you had so far?
• Feb 11th 2011, 06:46 PM
Prove It
(ii) Try evaluating the dot product...
• Feb 12th 2011, 04:13 AM
HallsofIvy
Any vector that is parallel to $\vec{i}+ 2\vec{j}$ is of the form $a\vec{i}+ 2a\vec{j}$. Any vector that is perpendicular to $3\vec{i}+ \vec{j}$ is of the form $b\vec{i}- 3b\vec{j}$. Find a and b so that $a\vec{i}+ 2a\vec{j}+ b\vec{i}- 3b\vec{j}= \vec{i}+ \vec{j}$