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#### karush

##### Well-known member

- Jan 31, 2012

- 3,241

*calculations and boxed answers are mine*

my question is with (iii) (provided the (i) and (ii) are correct.

from the diagram $cos \theta$ would be $\frac{OC}{OA}$ or $\frac{11.2}{13}$

but would need the the length of $OC$ to do so, what would be the best approach to get point $C$

we could convert $a$ and $b$ and to lines and find the intersection at $C$ hence $OC$.

but not sure how this could be done with just vectors