close
標題:
F.2 - F.3 Maths 一問
發問:
(1) [No figure]Given 2 circles of areas πr12 and πr22 (r1>r2) respectively. Express, in terms of r1 and r2,(a) the differece of the square,(b) the square of the difference,(c) the sum of the squareof their circumferences. And write your answers in factor form.(我唔明咩叫 difference of the square 同 square... 顯示更多 (1) [No figure] Given 2 circles of areas πr12 and πr22 (r1>r2) respectively. Express, in terms of r1 and r2, (a) the differece of the square, (b) the square of the difference, (c) the sum of the square of their circumferences. And write your answers in factor form. (我唔明咩叫 difference of the square 同 square of difference...) (2)Which is the lower rate: 630 l/h or 150 c.c./s? (l唔係一，係公升Litre) (我唔知1升等於等多c.c.) (3) (A+2)x + B≡ 0 , find the values of A and B. (4) [Figures aren't drawn to scale] 圖片參考：http://www.au18.net/maths/p23.JPG In the figure, AB = AC and AD = CD, ∠A=36, CD bisects ∠ACB. Prove that AD=BC. (5) 圖片參考：http://www.au18.net/maths/P89.JPG In the figure, △ABC is isosceles, ∠BAD = ∠CAD = ∠ACD. Find ∠ACD. 更新: π = PI
最佳解答:
其他解答:
F.2 - F.3 Maths 一問
發問:
(1) [No figure]Given 2 circles of areas πr12 and πr22 (r1>r2) respectively. Express, in terms of r1 and r2,(a) the differece of the square,(b) the square of the difference,(c) the sum of the squareof their circumferences. And write your answers in factor form.(我唔明咩叫 difference of the square 同 square... 顯示更多 (1) [No figure] Given 2 circles of areas πr12 and πr22 (r1>r2) respectively. Express, in terms of r1 and r2, (a) the differece of the square, (b) the square of the difference, (c) the sum of the square of their circumferences. And write your answers in factor form. (我唔明咩叫 difference of the square 同 square of difference...) (2)Which is the lower rate: 630 l/h or 150 c.c./s? (l唔係一，係公升Litre) (我唔知1升等於等多c.c.) (3) (A+2)x + B≡ 0 , find the values of A and B. (4) [Figures aren't drawn to scale] 圖片參考：http://www.au18.net/maths/p23.JPG In the figure, AB = AC and AD = CD, ∠A=36, CD bisects ∠ACB. Prove that AD=BC. (5) 圖片參考：http://www.au18.net/maths/P89.JPG In the figure, △ABC is isosceles, ∠BAD = ∠CAD = ∠ACD. Find ∠ACD. 更新: π = PI
最佳解答:
此文章來自奇摩知識+如有不便請留言告知
(1) Let the 2 radius be r and R(R is the bigger one). So their circumferences are 2pr and 2pR respectively (p stands for pi). (a) Difference of the square of their circumference = (2pR)^2 - (2pr)^2 = 4p^2(R^2 -r^2)= 4p^2(R+r)(R-r). (b)Square of their difference = (2pR-2pr)^2 = 4p^2(R-r)^2. (c)Sum of their square= (2pR)^2 + (2pr)^2 = 4p^2(R^2 + r^2). (2) One litre = 1000 cc. Therefore, 630l/h = 630 x 1000/3600 = 175 cc/s, so 150 cc/s is lower. (3)(A+2)x +B is identical to 0. That is A+2 = 0 , so A= -2. And B = 0. 2008-07-05 18:05:25 補充： (4) Angle A = 36, therefore angle B = (180-36)/2 = 72. AD=DC, therefore, angle ACD = 36, so angle CDB = 72. Therefore, CD=CB, but CD=AD, therefore CB=AD. 2008-07-05 18:10:25 補充： (5) Let angle BAD =angle CAD = angle ACD = x. Angle B=(180=x)/2. Therefore, x + x + x + (180-x)/2 = 180. 6x + 180 - x = 360, 5x = 180, therefore, x = 36= angle ACD. 2008-07-05 18:11:19 補充： Correction: Should be angle B=(180-x)/2.其他解答:
文章標籤
全站熱搜
留言列表
