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Pure Maths 12 today........

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was the radius 20 for last ques or 12 i dont remeber the question n well i did the vector one in a different way
 
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well for unit vector i firrst calculated vector AB the i calculated its magnitude interms of k n then equated it to 1
 
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the one in which eq of tangent to curve was x/k+k and eq of curve was 4y=x^2 and value of k was askd....try to remember......it was q3 i think..

I did it using another method but i got k=-1

i assumed that gradient of y=(1/k)x+c was 1/k
then i equated it with dy/dx of 4y=x^2
and by series of simultaneous equations i got k=-1
 
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radius
was the radius 20 for last ques or 12 i dont remeber the question n well i did the vector one in a different way
Radius was 20
But i'm not sure of the answers. I think that i made and error and got 34.6 for perimeter :(
 
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I did it using another method but i got k=-1

i assumed that gradient of y=(1/k)x+c was 1/k
then i equated it with dy/dx of 4y=x^2
and by series of simultaneous equations i got k=-1
yea k=-1 seems right....i was worried cause i didnt check my answers.......cuz i didnt have time to check em as my calculator stopped workin while solving q2...my luck:S
 
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Yeap it was in the direction of AB
Anyone remember the angle question.the one about arithematic progression?
I think i got 19 or something for n
 
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What was the question 11 for perimeter?
was it the two lines from 1.2 and [(the arc joining the two tangents together) or (the two lines form the tangents to the origin)?]
 
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if u use one wrong limits while calculating the volume obtained when the shaded region was rotated but everythin else is fine and u even added the pie..how many marks do u lose ?
 
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Yeap it was in the direction of AB
Anyone remember the angle question.the one about arithematic progression?
I think i got 19 or something for n

I got 18
a=3
d=2
sum= n/2 X (first + last)
360 = n/2 X (3+3+d(n-1))
720 = n(6+2(n-1))
720=6n+2n^2-2n
720= 4n + 2n^2
360=2n + n^2
(n-18)(n+20)=0
n=18
 
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if u use one wrong limits while calculating the volume obtained when the shaded region was rotated but everythin else is fine and u even added the pie..how many marks do u lose ?

Probably 2, 1 for wrong limits and 1 for wrong answer.
 
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how to do the equation of tangent. Do you hve to do dy/dx?

get Dy/Dx ,Substitute x=3 (I guess) to get the Gradient of tangent,substitute (3,1) to get C (not sure about the Coordinates tho,but that's the idea)
 
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Does anyone know how to answer Q10(b) the minimum value of the curve and also to prove that its a minimum?
 
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