Here's a recipe         a great turkey sandwich!

$\tan {70}^{\circ }+\tan {50}^{\circ }-\sqrt{3}\tan {70}^{\circ }\tan {50}^{\circ }$的值等于(   )

阅读下面这首诗，完成小题。
                                                                                                               春行即兴

                                                                                                                  李华
                                                                  宜阳城下草萋萋，涧水东流复向西。芳树无人花自落，春山一路鸟空啼。
（注：①写于安史之乱平息后不久。②宜阳城：唐代最大的行宫所在地。）