#2015_11 My class test problem -2

Geometry Level 4

$\large 12\sin(x)+5\cos(x)=2y^{ 2 }-8y+21$

If $$x$$ and $$y$$ are the solutions of the equation above, then what is the value of $$12\cot\left( \frac { xy }{ 2 } \right)$$ ?

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