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Find the value of cos(5*180/2-19*180/3)=? 

$\begin{array}{rcll} \cos{\left(5\cdot \frac{180}{2}-19\cdot \frac{180}{3} \right)} &=& \cos{\left(450 - 1140 \right)} \\ &=& \cos{ (-690 )} \\ &=& \cos{ (-690 +360 )} \\ &=& \cos{ (-330 )} \\ &=& \cos{ (-330 +360 )} \\ &=& \cos{ (30 )} \\ &=& \frac{ \sqrt{3} } {2} \\ &=& 0.86602540378 \\ \end{array}$