Let $\>\theta\>$ (in radians) be an acute angle in a right triangle and let $\>x\>$ and $\>y\>$, respectively, be the lengths of the sides adjacent to and opposite $\>\theta$. Suppose also that $\>x\>$ and $\>y\>$ vary with time.
At a certain instant $\>x = 2\>$ units and is increasing at $\>6\>$ unit/s, while $\>y = 2\>$ and is decreasing at $\>\frac {1} {8}\>$ units/s.
How fast is $\>\theta\>$ changing at that instant?

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