若 3sinθ+cosθ=103\sin \theta + \cos \theta = \sqrt{10}3sinθ+cosθ=10 ,则 tan(θ+π8)−1tan(θ+π8)\tan \left( {\theta + \frac{\pi }{8}}\right) - \frac{1}{\tan \left( {\theta + \frac{\pi }{8}}\right) }tan(θ+8π)−tan(θ+8π)1 的值为（ ）A. -7B. -14C. 17\frac{1}{7}71D. 27\frac{2}{7}72