Hi I was wondering if anyone could help me with this problem:(adsbygoogle = window.adsbygoogle || []).push({});

http://img209.echo.cx/img209/5105/vector5mm.png

In my textbook it says the answer is 1/2(p-q) but I don't understand how that answer is acheived. Any help would be appreciated.

Many thanks.

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# Vector problem

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