(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Rewrite the following vector in terms magnitude and angle: A force vector with a magnitude of 58 lb that is in the third quadrant with an x component whose magnitude is 30 lb.

3. The attempt at a solution

This is how I drew the problem:

[PLAIN]http://img535.imageshack.us/img535/4779/vecy.png [Broken]

Obviously, the answer to the first question asking the vector magnitude is just 58, but I'm having trouble getting the angle.. I tried:

[itex]cos(\theta) = \frac{-30}{58}[/itex]

[itex]\theta = cos^{-1}(\frac{-30}{58}) = 121.15^{\circ}[/itex]

But obviously that cannot be the answer (and it isn't..). So what am I doing wrong?

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# Homework Help: Finding a vector's angle

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