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標題:
locus(2)
發問:
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 ???
locus(2)
發問:
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 ???
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