9.(2023•松江区二模)已知π2<θ<π\frac{\pi }{2}<\theta <\pi2π<θ<π,且cosθ=−45\cos \theta =-\frac{4}{5}cosθ=−54,则tan2θ=\tan 2\theta =tan2θ=___−247-\frac{24}{7}−724___.