椭圆x²/9+y²/2=1的焦点为F1F2,点P在椭圆上,若|PF1|=4,角F1PF2的大小为
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椭圆x²/9+y²/2=1的焦点为F1F2,点P在椭圆上,若|PF1|=4,角F1PF2的大小为
椭圆x²/9+y²/2=1的焦点为F1F2,点P在椭圆上,若|PF1|=4,角F1PF2的大小为
椭圆x²/9+y²/2=1的焦点为F1F2,点P在椭圆上,若|PF1|=4,角F1PF2的大小为
|PF1|+|PF2|=2a=6
|PF1|=4
|PF2|=2
cos∠F1PF2=(|PF1|²+|PF2|²-4c²)/2|PF1||PF2|
=(16+4-28)/(2*4*2)
=-1/2
∠F1PF2=120°