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#101 Re: Exercises » Matriculation level - #n+4 » 2009-01-05 04:01:53

If this is equivalent to GCSE, the British education system is rubbish. Here, the trig questions wouldn't be encountered (usually) until AS/A level (16-18).

#102 Re: Dark Discussions at Cafe Infinity » University Offer » 2009-01-05 03:59:55

Tigeree wrote:

Bristol. Don't think urself 2 lucky! Wouldn't wanna jinx the chance. wink

I'm making my claim based on my other offers, offers given out in previous years, and the standard offer conditions.

#104 Re: Exercises » Matriculation level - #n+3 » 2009-01-04 01:08:45

I wasn't sure what 'matriculation level' was roll

#105 Re: Dark Discussions at Cafe Infinity » University Offer » 2009-01-04 01:07:02

Thank you smile

I'm definitely going with Cambridge as my firm. As for my insurance..... dunno

(still to hear from Bristol, but I'm expecting an offer)

#107 Re: Dark Discussions at Cafe Infinity » University Offer » 2009-01-02 22:24:40

Erm, rather unexpectedly, I received a letter this morning offering me a place to read Mathematics at Trinity College, Cambridge.

The conditions of the offer are pretty tough, though.

I'm absolutely over the moon smile

#108 Re: Help Me ! » Integral Proof » 2009-01-01 11:54:00

It wouldn't have anything to do with this, would it? http://en.wikipedia.org/wiki/Differentiation_under_the_integral_sign

#109 Re: Puzzles and Games » Neat problem » 2008-12-27 05:54:51

Jane, would you mind providing another hint to this?

#110 Re: Help Me ! » exact value » 2008-12-25 00:25:43

I think it's much quicker/easier/nicer to draw a triangle. The identities luca's used all come from triangles anyway.

#111 Re: Exercises » Daniel's Challenge Thread » 2008-12-24 13:41:50

Well the first part comes out from the sum of a geometric series:

Induction proves the second pretty quickly:

Obviously the first part could also be done (and more quickly) by induction, but I feel induction gets rid of the 'why' behind it. I'm sure you're going to show me a nicer way to do the second part smile

#112 Re: Help Me ! » composite functions » 2008-12-24 05:34:12

You're doing g first, then f, so the range of g must fit within the domain of f.

#113 Re: Dark Discussions at Cafe Infinity » University Offer » 2008-12-19 00:58:37

I received an offer from the University of Warwick the other day. They want AABb (I already have one A though) and either a 2 in STEP or a merit in AEA.

#114 Re: Help Me ! » 3x+5y=15 » 2008-12-17 03:41:48

This has an infinite number of solutions i.e. every point on the line y = -3/5x + 3.

Does the question specify that x and y are integers? (this still has an infinite number of solutions and all of them lie on that line, but at least it actually gives some work to do).

#115 Re: Help Me ! » projectiles up an inclined plane » 2008-12-09 08:59:54

Yep, just bothered to actually think about this.

Thanks.

Although, I seem to get that the x component of the acceleration is -gsinθ?

#117 Help Me ! » projectiles up an inclined plane » 2008-12-09 05:57:27

Daniel123
Replies: 5

Could someone very briefly explain the method involved in dealing with a projectile fired up an inclined plane? (i.e. how are velocities and weights resolved etc).

Quick responses would be greatly appreciated.

Thanks.

#118 Re: Help Me ! » Reduction formulae » 2008-12-07 05:34:32

I wrote:

, which I then integrated by parts (twice).

I also had to spot to rewrite

as
in the middle.

#120 Help Me ! » Reduction formulae » 2008-12-06 23:19:01

Daniel123
Replies: 3

Could someone give me a hint please?

Thanks.

#121 Re: Help Me ! » My brain isn't working » 2008-12-06 10:15:53

Ahh, thanks for sharing that smile

Also, "if three numbers are in arithmetic progression whose common difference is not a multiple of 3, at least one of them is divisible by 3" is pretty much what I stated in post #3 smile

#122 Re: Help Me ! » My brain isn't working » 2008-12-06 09:41:43

In fact, I've realised that if three numbers are in arithmetic progression, at least one of them is divisible by 3 unless the common difference is divisible by 3.

Easy to prove (by considering possible values of a and d (mod 3).

#123 Re: Help Me ! » My brain isn't working » 2008-12-06 09:37:19

Maybe the reason I can't prove it is because it's not true.

4, 7, 10.

#124 Help Me ! » My brain isn't working » 2008-12-06 09:25:57

Daniel123
Replies: 4

Prove that if three numbers are in arithmetic progression, at least one of them is divisible by 3.

#125 Re: Help Me ! » Chebyshev polynomials » 2008-12-06 08:17:51

Kurre wrote:

Cos2x+Cos3x=0
Cos2x=-Cos3x
Cos2x=Cos(pi-3x)
1)2x=3x-pi->x=pi->cosx=-1
2)2x=pi-3x->x=pi/5
looks like something is wrong with your equation...

You're right.

I'm actually rather stupid.

The factor should be (x+1), in which case x = -1 does work, as we can let x = cosθ (which we have to do anyway). Also,

Thanks smile

The point of the question was obviously to work in the trigonometric form, as the value of phi s.t

isn't obvious.

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