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Rob
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#1
Report Thread starter 16 years ago
#1
Since I know theres a few clever further maths chaps in here ... I'll put a question up i'm struggling with ...

s = ln(tan(Ø/2)

(a) ds/dØ = cosec(Ø)

x = 0, y = 0 at Ø = pi/2

(b) y = Ø - pi/2

(c) find an expression for x in terms of Ø

this is where i'm havin problems, i managed to do the rest, anyone know more than me ?

(taken from June 2002 P5 edexcel)

cheers, Rob
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Rob
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#2
Report Thread starter 16 years ago
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Hmm, aint that cute, my Psi's turn out all weird, but u get the idea ...

Rob
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hilly
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Report 16 years ago
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Hey,

I've done this one...which bit you stuck on exactly?
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Rich
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#4
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Originally posted by Rob
Since I know theres a few clever further maths chaps in here ... I'll put a question up i'm struggling with ...

s = ln(tan(Ø/2)

(a) ds/dØ = cosec(Ø)

x = 0, y = 0 at Ø = pi/2

(b) y = Ø - pi/2

(c) find an expression for x in terms of Ø

this is where i'm havin problems, i managed to do the rest, anyone know more than me ?

(taken from June 2002 P5 edexcel)

cheers, Rob
I use p to be psi.

dx/dp = (dx/ds)(ds/dp) (chain rule)

You should be able to see/already know that dx/ds = cos(p) (draw a triangle if necessary).

You know that ds/dp = cosec(p) from a).

So dx/dp = cos(p)cosec(p) = cot(p)

Integrate both sides with respect to dp...

Int(1 dx) = Int(cot(p) dp)
x = ln|sin(p)| + C

But x = 0, when p = pi/2, so:

x = ln|sin(p)|

Regards,
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Rob
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#5
Report Thread starter 16 years ago
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Hi,

cheers Richard .. i see it now. Theres a lot of using the chain rule in the P5 exams so i've seen, must look out for it more.

me no looky forwardy to exam

Rob
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