(Original post by adrienne_om)
Above from  http://www.thestudentroom.co.uk/show...1#post19333071
Maybe a correction here  I'm not sure  but I got a positive sign in the RHS of the second equation 
STEP I, II, III 2002 Solutions
Announcements  Posted on 



Seems Paper II Q1 has a bad solution here:
http://www.thestudentroom.co.uk/show...9#post18023769
No need to actually look at the question paper, Part ii) to this solution has some funky algebra!
The last few lines should be
The jump from the third line to the fourth still isn't all that clear but at least now it seems correct
EDIT: deleted my post below because I was wrong and the solution to Q2 seems correct. 
(Original post by Xero Xenith)
I think the result only holds for complex numbers modulus 1. 
(Original post by Xero Xenith)
Seems Paper II Q1 has a bad solution here:
http://www.thestudentroom.co.uk/show...9#post18023769
No need to actually look at the question paper, Part ii) to this solution has some funky algebra!
The last few lines should be
The jump from the third line to the fourth still isn't all that clear but at least now it seems correct
EDIT: deleted my post below because I was wrong and the solution to Q2 seems correct. 
(Original post by Xero Xenith)
Seems Paper II Q1 has a bad solution here:
http://www.thestudentroom.co.uk/show...9#post18023769
No need to actually look at the question paper, Part ii) to this solution has some funky algebra!
The last few lines should be
The jump from the third line to the fourth still isn't all that clear but at least now it seems correct
EDIT: deleted my post below because I was wrong and the solution to Q2 seems correct. 
(Original post by Extricated)
Probably being a bit stupid here but how did you go from 1sqrt(1cos^2 x) to 1cos2x?(denominator line 1, to denominator line2), I think the sin^2(2x) has been replaced by sin^2x in line 1 accidentally.
(Original post by sonofdot)
Good spot, fixed 
(Original post by Extricated)
Probably being a bit stupid here but how did you go from 1sqrt(1cos^2 x) to 1cos2x?(denominator line 1, to denominator line2), I think the sin^2(2x) has been replaced by sin^2x in line 1 accidentally. Ofcourse doesn't affect final answer, but could lead to a little confusion 

(Original post by yukki0822)
sorry im really confused that why does the modulus of r equal to 1? 
For II, Q10, I believe there's an error in the final part  the should have an x attached, which makes the final answer 81/40. I also get this answer through an entirely different approach to the question:
Spoiler:Show
Differentiate implicitly:
When T is stationary, , so
Plug this back into the original equation:
This gives maxima/minima at T = 0 and T = 3. T = 0 is obviously impossible, so T must equal 3, as required.
For the second part, use a trapezium to calculate the final speed of the second competitor, and use this to work out the acceleration:
And so the acceleration is then .
, which means that the speed in the second part is 14.5. Next, find the time when they are moving at equal speed, as this is when maximum displacement occurs:
This is greater than 0.75 so is fine. Then, calculate the distances for each:
Subtracting one from the other yields the final answer

(Original post by SimonM)
STEP I, Question 4
Spoiler:Show
Therefore the equation of the tangent is
Since is a solution
This gives us the equation,
We have so the only intersections are 0 and 1.
We have
(given)
The area under the tangent is a trapezium with area
Since the graph is always above it, we get which is what we want to show.
Considering the half closest to the y axis, and revolving it around that axis we get:
and
Therefore 
Regarding STEP III / 2002 / Q8, i had thought that Dadeyemi gave an excellent answer, but a student of mine was seeking clarification for the first part regarding the periodicities of the argument and the tangent. I looked at the problem more closely just now, and agree that it needs to be tightened up a little. Here is my little "patch":
Let . It has already been shown that
Hence (*)
Since , we have that
and so
We check the remaining cases where as follows (draw your own diagrams):
all the best for your STEP exams tomorrow! 
(Original post by Generic Name)
Does this graph have an oblique asymptote? 
do you have to assume that the means take the positive root beacause you want it to be a function?
It is also confusing for me because after every step the possibilities are many for example the step nota bene has just made.
It could also be:
Summary if this question meant take the power of half to mean take the positive square root i would have no problems
but i am not sure if this is so.
Could you please clarify? 
(Original post by nahomyemane778)
this was for question 3 step 1 I am having some trouble with it because i do not not know how to interpret the power
do you have to assume that the means take the positive root beacause you want it to be a function?

(Original post by davros)
Yes  you've answered your own question 
(Original post by Dadeyemi)
Some more;
Did these quite a while ago I'm afraid some may be partial solutions. 
Re: 2002/III/Q8
Dadeyemi gave an excellent solution and SingaporeCantab had a point on the periodicity. Notice that the periodicity of complex numbers is 2n(pi) because of the specific signs for the real part and the imaginary part. Need extra care in using the tan function where the periodicity is n(pi), e.g cis(pi/4) is not equal to cis(pi/4 + pi) though tan(pi/4) = tan(pi/4+pi). I think the patch is not entirely correct.
My patch to the "patch": I think it is sufficient to say that (theta1 + theta2  pi)/2 has a range (3pi/2, pi/2). When (theta1 + theta2  pi)/2 is in the range (3pi/2, pi], we need to add 2pi (i.e. n=1) to bring it back to the domain of (pi,pi]. Otherwise n=0. 
k= 1/2a x {1 +/ sqrt[(1+3a)/(1a)]}
= 1/2a x {1 +/ sqrt[1+ 4a/(1a)]}
since 4a/(1a)>0 so the sqrt >1, and k>0, hence cannot take the negative sqrt.
k = 1/2a x {1 + sqrt[1+ 4a/(1a)]}
Reply
Submit reply
Register
Thanks for posting! You just need to create an account in order to submit the post Already a member? Sign in
Oops, something wasn't right
please check the following: