- #1
Driverfury
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Homework Statement
Ok guys, I'm studying Physics and I started, of course, by learning about vectors.
So I have this problem:
There are two vectors: A (its length is 3 m) and B (its length is 4 m). I have not other informations about them.
I want to know how I can dispose them to get a vector S (which is A + B) such as:
a) its length is 7 m.
b) its length is 1 m.
c) its length is 5 m.
Now, I know that the points a and b are obvious but I want a rigorous solution which is valid for point c and for every other length of the vector S.
Homework Equations
Note[/B]: From now on when I write a I mean the length of the vector A. When I write b I mean the length of the vector B. Let's call o the agle between them.
Maybe this equation will be useful.
cos(o) = (A . B) / (a b)
The Attempt at a Solution
I tried but I cannot evaluate the scalar product A . B because it is equals to (a b cos(o)). And if I replace it in the equation I have:
cos(o) = (a b cos(o)) / (a b) = cos(o)
I need your help.