题目

在平面直角坐标系中，直线的参数方程为（其中为参数）．以坐标原点为极点，轴正半轴为极轴建立极坐标系并取相同的单位长度，曲线的极坐标方程为．（Ⅰ）求和的直角坐标方程；（Ⅱ）过点作直线的垂线交曲线于，两点，求. 答案：【答案】（Ⅰ），（Ⅱ）【解析】（I）利用加减消元法消去的参数，求得的直角坐标方程.对的极坐标方程两边乘以，化简后得到的直角坐标方程.（II）设出过点与直线垂直的直线的参数方程，代入的直角坐标方程，化简后写出韦达定理，利用直线参数的几何意义求得的值.解：（Ⅰ）直线的参数方程为 完形填空 Dear Alice, 　　How are you doing?It's very nice 　　1　　 you to write 　　2　　 me．From your letter I 　　3　　 a lot about you and your school．Now let me 　　4　　 you something about me and my school． 　　I'm thirteen years old．I'm in Class Two, Grade One of Yuli Middle School．My father is a 　　5　　．He teaches Chinese．My mother is a doctor．I 　　6　　 early every morning and 　　7　　 English． 　　　　8　　 school is very big．It 　　9　　 1,500 students and 160 teachers．Both the teachers and students 　　10　　 hard．We're working 　　11　　 the people．Please come to my school when you have 　　12　　． (1) [　　] A． on B． of C． for D． to (2) [　　] A． of B． from C． to D． on (3) [　　] A． study B． tell C． know D． talk (4) [　　] A． say B． tell C． speak D． talk (5) [　　] A． worker B． teacher C． student D． doctor (6) [　　] A． have lessons B． get up C． go to bed D． come here (7) [　　] A． see B． read C． watch D． look (8) [　　] A． Your B． Their C． Our D． No (9) [　　] A． has B． have C． is D． counts (10) [　　] A． work B． play C． are D． be (11) [　　] A． to B． for C． of D． at (12) [　　] A． money B． friends C． holiday D． time