7×0.7=____
7×0.7×0.7=____
7×0.7×0.7×0.7=____
7×0.7×0.7×0.7×0.7=____
7×0.7×0.7×0.7×0.7×0.7…____
双曲线 的两条渐近线互相垂直,则双曲线的离心率为____
下列记录的实验现象与事实不相符的是( )