2022年高考数学天津7 |
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2022-12-16 20:38:08 |
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(5分)已知抛物线$y^{2}=4\sqrt{5}x$,$F_{1}$,$F_{2}$分别是双曲线$\dfrac{x^2}{a^2}-\dfrac{y^2}{b^2}=1(a > 0,b > 0)$的左、右焦点,抛物线的准线过双曲线的左焦点$F_{1}$,与双曲线的渐近线交于点$A$,若$\angle F_{1}F_{2}A=\dfrac{\pi }{4}$,则双曲线的标准方程为( ) A.$\dfrac{x^2}{10}-y^{2}=1$ B.$x^{2}-\dfrac{y^2}{16}=1$ C.$x^{2}-\dfrac{y^2}{4}=1$ D.$\dfrac{x^2}{4}-y^{2}=1$ 分析:先由抛物线方程的准线方程,得双曲线的半焦距$c$,再联立抛物线准线方程与双曲线的渐近线方程解得$\vert y_{A}\vert$,接着由$\angle F_{1}F_{2}A=\dfrac{\pi }{4}$,可得$\vert y_{A}\vert =\vert F_{1}F_{2}\vert$,从而得$b=2a$,最后再通过$c^{2}=a^{2}+b^{2}$建立方程即可求解. 解:由题意可得抛物线的准线为$x=-\sqrt{5}$,又抛物线的准线过双曲线的左焦点$F_{1}$, $\therefore c=\sqrt{5}$,联立$\left\{\begin{array}{l}{x=-c}\\ {y=-\dfrac{b}{a}x}\end{array}\right.$,可得$\vert y_{A}\vert =\dfrac{bc}{a}$,又$\angle F_{1}F_{2}A=\dfrac{\pi }{4}$, $\therefore \vert y_{A}\vert =\vert F_{1}F_{2}\vert$, $\therefore$$\dfrac{bc}{a}=2c$,$\therefore b=2a$,$\therefore b^{2}=4a^{2}$, 又$c^{2}=a^{2}+b^{2}$, $\therefore 5=a^{2}+4a^{2}$, $\therefore a^{2}=1$,$b^{2}=4$, $\therefore$双曲线的标准方程为${x}^{2}-\dfrac{{y}^{2}}{4}=1$. 故选:$C$. 点评:本题考查抛物线的性质与双曲线的性质,方程思想,属基础题.
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