If
\[ \cos x + \sin x = \frac{1}{2} \]
and
\[ 0 < x < \pi, \text{ then } \tan x = \ ? \]
At 700 K, the equilibrium constant $K_e$ for the reaction $ \text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) $ is 0.2 mol L$^{-2}$. What is the value of $K$ for the reverse reaction?