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[Core] 急!求數學勁人解這題數 唔識做

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急!求數學勁人解這題數 唔識做

https://drive.google.com/open?id=0B6vWADaPmgtiaVlSRFFrVlI3WWM

[ 本帖最後由 mathsgogogo 於 2017-3-13 05:47 PM 編輯 ]
   

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求a iii 同點搵到coordinates of A

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睇唔到幅圖

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再整過

[ 本帖最後由 mathsgogogo 於 2017-3-13 05:44 PM 編輯 ]

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P= (-3,3) A= (-2,2) D= (-1,1) C= (1/3, 7/3)     3x^2+ 3y^2 -2x-14y+6=0    T= (3/5, 21/5)       x+7y-30=0
involve some very elementary geometry and trigo; should be easy

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aiii is very obvious:   Take O as (0, 0),   Big circle:  x^2 + y^2 = R^2   Small circle: (x-0)^2 + (y-d)^2=r^2   where D= (0,d)  solving this system of eqs simultaneously will reduce it to a linear eq,; hence touching at one point

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但coordinates of A 點樣直接睇出來,ans應該係(-1,5)?



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yes A is definitely (-1,5) , I copied the wrong coordinates from my rough working! Just from the diagram, (-2,2) is an impossible answer!

Q is (3,-3) so P is (-3,3) due to symmetry so OP is 135 deg to x-axis & as PA is right angled to OP so PA is 45 deg to x-axis and as PA=a=2sqrt2 so A is acos45 to right of P and also asin45 above P i.e. 2 units to the right and 2 units above P so A is (-3+2, 3+2) = (-1,5)

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