则
|
|F1F2|=4．
∴cos∠F1PF2=
| m2+n2-42 |
| 2mn |
| (m+n)2-2mn-42 |
| 2mn |
| 24-6-16 |
| 2×3 |
| 1 |
| 3 |
故选：D．
椭圆x26+y22=1和双曲线x23-y2=1的公共焦点为F1，F2，P是两曲线的一个交点，那么cos∠F1PF2的值是（ ） A.13 B.23 C.73 D.14
椭圆
+
=1和双曲线
-y2=1的公共焦点为F1，F2，P是两曲线的一个交点，那么cos∠F1PF2的值是（ ）
A.
B.
C.
D.
| x2 |
| 6 |
| y2 |
| 2 |
| x2 |
| 3 |
A.
| 1 |
| 3 |
B.
| 2 |
| 3 |
C.
| 7 |
| 3 |
D.
| 1 |
| 4 |
数学人气：200 ℃时间：2019-08-20 07:39:58
优质解答
设P是双曲线右支上的一点，设|PF1|=m，|PF2|=n．
则
，解得mn=3．
|F1F2|=4．
∴cos∠F1PF2=
=
=
=
．
故选：D．
则
|F1F2|=4．
∴cos∠F1PF2=
故选：D．
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