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Can someone help me, I stop following the example when you get 1/3 ... I dont get the last 3 lines of the this.
Original post by Proflash



Can someone help me, I stop following the example when you get 1/3 ... I dont get the last 3 lines of the this.

You have that tan(arctan3+2arctan2)=tan(arctan13+kπ),kZ\tan (\arctan 3 + 2 \arctan 2) = \tan \left( \arctan \frac{1}{3} + k \pi \right), k \in \mathbb{Z} as the tan graph is periodic with integer multiples of π\pi

But, if you take principle values, you know if tanθ=3π4<θ<π2\tan \theta = 3 \Rightarrow \frac{\pi}{4} < \theta < \frac{\pi}{2} (because tanπ4=1\tan \frac{\pi}{4} = 1 and limθπ2tanθ=\lim_{\theta \to \frac{\pi}{2}} \tan \theta = \infty so the value of tanθ=3\tan \theta = 3 has to be sandwiched between these two. The same goes for tanϕ=2\tan \phi = 2

As π4<θ<π2,π4<ϕ<π22π4<2ϕ<π34π<θ+2ϕ<32π\frac{\pi}{4} < \theta < \frac{\pi}{2}, \frac{\pi}{4} < \phi < \frac{\pi}{2} \Rightarrow \frac{2 \pi}{4} < 2 \phi < \pi \Rightarrow \frac{3}{4} \pi < \theta + 2 \phi < \frac{3}{2} \pi (adding the lower and upper bounds)

Thus, from the given range, we have that k=1θ+2ϕ=π+arctan13k = 1 \Rightarrow \theta + 2 \phi = \pi + \arctan \frac{1}{3}

arctan13=αtanα=13cotα=3α=arccot3\arctan \frac{1}{3} = \alpha \Rightarrow \tan \alpha = \frac{1}{3} \Leftrightarrow \cot \alpha = 3 \Rightarrow \alpha = arccot 3
(edited 10 years ago)
Reply 3382
Original post by Proflash



Can someone help me, I stop following the example when you get 1/3 ... I dont get the last 3 lines of the this.


In the line that says BUT.... they have basically ammended the range:

θ+2ϕ \theta+2\phi where θ=0.25π\theta =0.25\pi and ϕ=0.25π \phi=0.25\pi you end up with 14π+2(14π)=(34π)\frac{1}4\pi+2(\frac{1}4\pi{}){}=(\frac{3}{4} \pi)

Also for the end of the range θ=0.5π\theta =0.5\pi and ϕ=0.5π\phi=0.5\pi so end of range is: 12π+2(12π)=(32π)\frac{1}2\pi+2(\frac{1}{2}\pi)=(\frac{3}{2} \pi)

(34)π<θ+2ϕ<(32)π\therefore (\frac{3}{4})\pi< \theta+ 2\phi <(\frac{3}{2})\pi

Felix has the rest covered :P
(edited 10 years ago)
Original post by Proflash



Can someone help me, I stop following the example when you get 1/3 ... I dont get the last 3 lines of the this.


Here is an alternative way you may like to approach the question, using complex numbers:

(1+3i)(3i)(1+2i)2=(6+8i)(3+4i) (1+3i)(3-i)(1+2i)^2 = (6+8i)(-3+4i)

=(50) = (-50)

So we have:

(1+3i)(3i)(1+2i)2=50 (1+3i)(3-i)(1+2i)^2 = -50

Take arguments of both sides:

arg[(1+3i)(3i)(1+2i)2]=arg(50) arg[(1+3i)(3-i)(1+2i)^2] = arg(-50)

arctan3+2arctan2arctan13=π arctan3+2arctan2-arctan\frac{1}{3} = \pi

arctan3+2arctan2=π+arccot3 arctan3 + 2arctan2 = \pi +arccot3
Can someone help me solve this:
ex=10e^{-x}=10

I tried to take logs both sides but I don't seem to get the answer in the textbook which says

ln(0.1)\ln (0.1)

Thanks
:biggrin:

Original post by Westeros
Can someone help me solve this:
ex=10e^{-x}=10

I tried to take logs both sides but I don't seem to get the answer in the textbook which says

ln(0.1)\ln (0.1)

Thanks
:biggrin:



e^(-x) = 10
ln10 = -x
x = -ln10

Power rule.

Spoiler



Make sense?
Original post by L'Evil Fish
e^(-x) = 10
ln10 = -x
x = -ln10

Power rule.

Spoiler



Make sense?


Thank you :colondollar: *dumb moment*
Do unis care about the average UMS of AS maths more than the average of AS and A2 combined together?
Original post by Westeros
Thank you :colondollar: *dumb moment*


Np :yy:
Original post by MAyman12
Do unis care about the average UMS of AS maths more than the average of AS and A2 combined together?


If you've done both before you apply then both.
And if by Universities you mean Oxbridge (maybe warwick/imperial).
Most unis don't look at UMS, only grades.
(edited 10 years ago)
Original post by joostan
If you've done both before you apply then both.
And if by Universities you mean Oxbridge (maybe warwick/imperial).
Most unis don't look at UMS, only grades.


Yes I meant Oxbridge. You mean that I don't need to worry that my average UMS in AS maths is >95 if I've applied after finishing my A Level?

If I got A*A*A would they care about my UMS?
I feel really stupid:tongue:
Original post by MAyman12
Yes I meant Oxbridge. You mean that I don't need to worry that my average UMS in AS maths is >95 if I've applied after finishing my A Level?

If I got A*A*A would they care about my UMS?
I feel really stupid:tongue:


UMS is far less important than grades.
Cambridge go by module scores - I imagine an average of 90+ is sufficient - they've got their own methods of selection like STEP + interview etc.
Oxford prefer GCSEs, though there's also the MAT to do. :smile:
EDIT: Malicious and petty negging, really? :erm:
(edited 10 years ago)
Original post by joostan
UMS is far less important than grades.
Cambridge go by module scores - I imagine an average of 90+ is sufficient - they've got their own methods of selection like STEP + interview etc.
Oxford prefer GCSEs, though there's also the MAT to do. :smile:


So by modules scores you mean A B C etc...? And about STEP, should I prepare for it if I'm applying for NatSci (Physics)?
(edited 10 years ago)
Original post by MAyman12
Oh okay take your time:yy: Sorry, if I'm asking too much:redface:

Here's the best that I've managed to come up with to show that the recurring radical converges and even then, I'm not sure if my logic is correct/ rigorous enough...

Spoiler

(edited 10 years ago)
Original post by joostan
UMS is far less important than grades.
Cambridge go by module scores - I imagine an average of 90+ is sufficient - they've got their own methods of selection like STEP + interview etc.
Oxford prefer GCSEs, though there's also the MAT to do. :smile:


Original post by MAyman12
Do unis care about the average UMS of AS maths more than the average of AS and A2 combined together?


Several things:

1 - Whilst Cambridge is the main university that asks for modular marks it is not the only one. I was asked to submit UMS by Durham, and I don't think it's unheard of for Imperial to ask.
2 - For Cambridge an average of 90% in Maths is below average. I was told in all seriousness by a liaisons officer who came to our school that the average I applied with (97%) was "standard", which was borne out by the fact Maths doesn't have auto-pooling. This fits into point 3) - for Cambridge the UMS is very important, as there's a huge difference between 81% average and 100%.
4 - Oxford preferring GCSE's is an urban myth, and I certainly don't think they put as much emphasis on them as some people think. Firstly, Oxford have the MAT scores which are significantly more important. In addition, Oxford interviews usually happen over a week (You have to stay at Oxford) and so they have more interview data to work with, whereas you're unlucky if you don't do all your Cambridge interviews in a single day.
5 - Cambridge will care about every Maths module you've taken. I think (But do not know) that Pure and Mechanics take precedence; I believe you'd get away with 80 in D1 a lot easier than 80 in FP1, for example. I think that, if you've taken AS and A2 modules simultaneously at AS (e.g. your school teaches Maths the first year and Further the second) they are given equal precedence (Treated the same as people taking AS Maths and Further together), but if you're applying after completing A Levels then your 2nd year modules are expected to be higher to show a progression.
Original post by DJMayes
S.


Do you think my average will be okay as I'm not applying for maths?

Hopefully it'll be 92+%
Original post by Felix Felicis
Here's the best that I've managed to come up with to show that the recurring radical converges and even then, I'm not sure if my logic is correct/ rigorous enough...

Spoiler



Awesome.:biggrin:

Thank you, I'm sure that it took some time to write.:tongue: It would be better If you used less symbols, as it confuses me:redface:

How do you know such methods?
(edited 10 years ago)
Original post by DJMayes
Several things:

1 - Whilst Cambridge is the main university that asks for modular marks it is not the only one. I was asked to submit UMS by Durham, and I don't think it's unheard of for Imperial to ask.
2 - For Cambridge an average of 90% in Maths is below average. I was told in all seriousness by a liaisons officer who came to our school that the average I applied with (97%) was "standard", which was borne out by the fact Maths doesn't have auto-pooling. This fits into point 3) - for Cambridge the UMS is very important, as there's a huge difference between 81% average and 100%.
4 - Oxford preferring GCSE's is an urban myth, and I certainly don't think they put as much emphasis on them as some people think. Firstly, Oxford have the MAT scores which are significantly more important. In addition, Oxford interviews usually happen over a week (You have to stay at Oxford) and so they have more interview data to work with, whereas you're unlucky if you don't do all your Cambridge interviews in a single day.
5 - Cambridge will care about every Maths module you've taken. I think (But do not know) that Pure and Mechanics take precedence; I believe you'd get away with 80 in D1 a lot easier than 80 in FP1, for example. I think that, if you've taken AS and A2 modules simultaneously at AS (e.g. your school teaches Maths the first year and Further the second) they are given equal precedence (Treated the same as people taking AS Maths and Further together), but if you're applying after completing A Levels then your 2nd year modules are expected to be higher to show a progression.


Just to ask for some input for my current scenario, for M1 I messed up badly (well not bad as in bad but you get the point) I got 63/75 (without method marks) which no doubt will probably be around 80-84ums. I also failed to complete S1 in time and as a result I couldn't have time to answer questions, dropping down to 66/75 which is give or take around 86-88 ums, will these two bad modules affect my overall chances?.

S2 went well and expecting about 95 ums, C2 I got 100ums so my maths average is looking about 95% whilst further maths about 91% (if FP1 is 98+). The main problem I see, is my mechanics, this is the only mechanics I have to show to Cambridge and I did fairly badly in it, I will apply regardless but I was wondering if you could use your advice to give me knowledge and apply it to my current situation.

On a more bright note, expecting to get just about 90ums for economics, and an overall A for history. (which may or may not help)
(edited 10 years ago)
Original post by DJMayes
Several things:

Spoiler



I think I flunked my M1 exam this summer,though I was quite able at mechanics and was expecting a 100. But, I got really nervous in the exam and now I'm expecting 85 or something if lucky. Would they bother with that?

I'm applying for Physics-NatSci, what UMS scores are they expecting from me in Maths and FM (I know that maths is extremely important for physics, actually it's impossible to do proper physics without it)?

Thank you for explaining things.:biggrin:
(edited 10 years ago)
Original post by Robbie242
Just to ask for some input for my current scenario, for M1 I messed up badly (well not bad as in bad but you get the point) I got 63/75 (without method marks) which no doubt will probably be around 80-84ums. I also failed to complete S1 in time and as a result I couldn't have time to answer questions, dropping down to 66/75 which is give or take around 86-88 ums, will these two bad modules affect my overall chances?.

S2 went well and expecting about 95 ums, C2 I got 100ums so my maths average is looking about 95% whilst further maths about 91% (if FP1 is 98+). The main problem I see, is my mechanics, this is the only mechanics I have to show to Cambridge and I did fairly badly in it, I will apply regardless but I was wondering if you could use your advice to give me knowledge and apply it to my current situation.

On a more bright note, expecting to get just about 90ums for economics, and an overall A for history. (which may or may not help)


We were both were screwed by M1:tongue:

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