# Wrong answer in textbook

**1. The problem statement, all variables and given/known data**

(Problem about a collision) (…). What then is their velocity in (a) unit-vector notation and as (b) magnitude and (c) angle.

I will not post the problem due to copyright issues and that it is absolutely pointless now.

**3. The attempt at a solution**

I was able to solve (a) and (b).

However, my answer for (c) differs from that of the textbook.

[tex]\text{a)} \;(2.67 \;\text{m/s})\hat{i}+(-3.00 \;\text{m/s})\hat{j}[/tex]

[tex]\text{b)} \;4.01 \;\text{m/s}[/tex]

[tex]\text{c)} \;\theta{} = \tan^{-1}\left(-\frac{3.00}{2.67}\right)=-0.845397=-48.4^{\circ{}}[/tex]

While the book provides **+**48.4° as the angle.

Am I correct? You can solve (c) from (a) and (b) [my answers are identical to those of the book].

It is from Fundamentals of Physics (Extended) – 9th ed.

http://ift.tt/1iIQjNA

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