P4 itteration Watch

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#1
Report Thread starter 13 years ago
#1
i've done this question, with, and without the markscheme, an i've no idwa where i'm going wrong, or whether the markscheme is wrong HELP!!!

http://math.mdsalih.com/Data/index.p...thematics%2FP4

have a look what the markschemes say
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London Prophet
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#2
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#2
Which question (It's been a year since p4 and the course seems different but i'll help if i can)
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Gaz031
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#3
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(Original post by Phil23)
i've done this question, with, and without the markscheme, an i've no idwa where i'm going wrong, or whether the markscheme is wrong HELP!!!
For (a) I get 2.65(3sf).
For (b) I get 2.91(3sf).
Is it (a) or (b) that you don't like?
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Jonny W
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#4
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(a)
f(2) = -1.5136
f(pi) = 1.1416

The straight line between (2, -1.5136) and (pi, 1.1416) intersects the x-axis at

2 + [1.5136/(1.5136 + 1.1416)] (pi - 2) = 2.65

(b)
f'(x) = 1 + 4cos(2x)

2.8 - f(2.8)/f'(2.8) = 2.91
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#5
Report Thread starter 13 years ago
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(Original post by Jonny W)

f'(x) = 1 + 4cos(2x)

2.8 - f(2.8)/f'(2.8) = 2.91

can you show me teh steps - i'm still not getting that answer; i dont believe it - what am i doing wrong:eek:

pk
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#6
Report Thread starter 13 years ago
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(Original post by Phil23)
can you show me teh steps - i'm still not getting that answer; i dont believe it - what am i doing wrong:eek:

pk
i'm getting 2.600
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Jonny W
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#7
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f(2.8) = -0.46253
f'(2.8) = 4.10226

2.8 - (-0.46253)/4.10226 = 2.91
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#8
Report Thread starter 13 years ago
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(Original post by Jonny W)
f(2.8) = -0.46253
f'(2.8) = 4.10226

2.8 - (-0.46253)/4.10226 = 2.91
i don't believe it guys..its not a typo, not the differentiation, but i had my calculators on DEGREE MODE!!!! - aghhh...done that twice in my life now :rolleyes:

cheers for your time

Pk
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Gaz031
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#9
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(Original post by Phil23)
i don't believe it guys..its not a typo, not the differentiation, but i had my calculators on DEGREE MODE!!!! - aghhh...done that twice in my life now :rolleyes:

cheers for your time

Pk
Heh, i've done that before but luckily always get stupid answers like an angle of 80 radians so I realise quickly. Now I keep it in radian mode unless i'm doing vectors or the question specifically asks for things in degrees.
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