已知F1,F2是双曲线E x2a2−y2b2=1 的左,右焦点,点M在E上,M F1与 x 轴垂直,sin ∠MF2F1=13 ,则E的离心率为( )
读公转示意图,并回答下列问题。
---What color_____ the cats?---I think ________white and black.
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