標題:

locus(2)

發問:

免費註冊體驗

 

此文章來自奇摩知識+如有不便請留言告知

a line is drawn from a fixed point C(-4,1) to a variable point B on the y-axis.From point B, a line perpendicular to BC is drawn to cut the x-axis at A.P(x,y)is the mid point of AB. a.)Express the coordinates of A and B in term of x and y. b.)Find the equation of the locus of P.

最佳解答:

a)Let A be (a , 0) , B be (0 , b) ,Since P(x,y)is the mid point of AB ,x = (a + 0)/2 = a/2 a = 2xy = (0 + b)/2 = b/2 b = 2yA is (2x , 0)B is (0 , 2y) b)Since CB 丄 BA ,Slope of CB * Slope of BA = - 1(1 - 2y) / (- 4 - 0) * (2y - 0) / (0 - 2x) = - 1(1 - 2y)(2y) = (- 1)(- 4)(- 2x)2y - 4y2 = - 8x2y2 - y - 4x = 0 The locus of P(x , y) is 2y2 - y - 4x = 0 2011-04-19 20:40:07 補充: The question say : From point B, a line {perpendicular} to BC is drawn ......

其他解答:

why CB 丄 BA ???
arrow
arrow

    香港美食推薦 發表在 痞客邦 留言(0) 人氣()