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September 20, 2025, 10:51:33 am
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Author Topic: Insanely hard Q.  (Read 6231 times)  Share 

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MBBS

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Insanely hard Q.
« on: October 04, 2010, 09:34:32 pm »
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cos 4A+1 is equal to

A. 2(cos A-1)2
B. 2cos22A
C. cos2A
D.sin2A


Please help, I'm totally lost.
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vea

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Re: Insanely hard Q.
« Reply #1 on: October 04, 2010, 09:38:17 pm »
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I'm not up to trig identities in GMA yet but I'll give it a shot.






Which is B :\
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sb3700

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Re: Insanely hard Q.
« Reply #2 on: October 04, 2010, 09:39:52 pm »
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Double angle formulas are:



So we can simplify:

(using X = 2A)

and

This means B is correct. It's a good idea to check the other options as well (just in case), by applying the double angle formulas again to both of the above forms.
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Re: Insanely hard Q.
« Reply #3 on: October 05, 2010, 01:09:46 am »
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It's no longer insanely hard once u know how to do it =p
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MBBS

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Re: Insanely hard Q.
« Reply #4 on: October 20, 2010, 02:25:40 pm »
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Ok thanks guys, our teacher is utterly useless for GMA, I have never said that about another teacher but this guys is extermely nice just well past it. Where can I learn more about Chapter 11 of the GMA book? It's theorey compnents aren't very comprehensive.
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pi

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Re: Insanely hard Q.
« Reply #5 on: October 24, 2010, 07:19:17 pm »
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which GMA book?
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cohen

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Re: Insanely hard Q.
« Reply #6 on: October 24, 2010, 08:45:08 pm »
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Im guessing it's Essential General Maths Advanced (That's the book we're using, and chapter 11 is on this sort of stuff).

And at least your teacher is using the book, in GMA at my school, we've only done 2 chapters from the book, and the rest is stuff he makes up.
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pi

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Re: Insanely hard Q.
« Reply #7 on: October 25, 2010, 06:05:12 pm »
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Quote from: cohen on October 24, 2010, 08:45:08 pm
Im guessing it's Essential General Maths Advanced (That's the book we're using, and chapter 11 is on this sort of stuff).

And at least your teacher is using the book, in GMA at my school, we've only done 2 chapters from the book, and the rest is stuff he makes up.

lol, we only did a few chapters (there are over 20!). this semester we did complex numbers (from maths quest 12 spesh), mechanics (from maths quest 12 spesh), trig and proofs and loci....

pretty bludge really
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pi

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Re: Insanely hard Q.
« Reply #8 on: November 14, 2010, 03:55:28 pm »
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Quote from: MBBS on October 04, 2010, 09:34:32 pm
cos 4A+1 is equal to

A. 2(cos A-1)2
B. 2cos22A
C. cos2A
D.sin2A


Please help, I'm totally lost.

lol, this question came up on my GMA exam this year (MHS) question 1 in multiple choice section
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MBBS

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Re: Insanely hard Q.
« Reply #9 on: November 14, 2010, 04:09:27 pm »
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It's pretty easy these days, worked a few hours on it and it's really simple :P

I ran out of time for my GMA exam cos I was sooooo bloody pedantic about the earlier questiosn making sure full marks... Not too worried content was easy and others found it hard, so just gotta work on my timing.
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pi

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Re: Insanely hard Q.
« Reply #10 on: November 14, 2010, 04:16:19 pm »
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Quote from: MBBS on November 14, 2010, 04:09:27 pm
It's pretty easy these days, worked a few hours on it and it's really simple :P

I ran out of time for my GMA exam cos I was sooooo bloody pedantic about the earlier questiosn making sure full marks... Not too worried content was easy and others found it hard, so just gotta work on my timing.

same (except our exam was a killer), only 4 people in our year level (of 200 GMA kids) finished the whole exam (tech-free) -and that includes math olympiads and AMC prize winners! felt like crap afterwards...

got that question though
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MBBS

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Re: Insanely hard Q.
« Reply #11 on: November 14, 2010, 04:20:33 pm »
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Jesus Christ!

200 GMA kids, we have like 30!

The actual subject has been pretty easy thus far though.
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pi

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Re: Insanely hard Q.
« Reply #12 on: November 14, 2010, 04:25:43 pm »
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Quote from: MBBS on November 14, 2010, 04:20:33 pm
Jesus Christ!

200 GMA kids, we have like 30!

The actual subject has been pretty easy thus far though.

our subject co-ordinator is some Indian Lankan guy with a phD in pure maths (yep, wtf!), and he made us do a third of the yr 12 course as well as the GMA course. Just for fun, he put random unit 1 methods stuff in as well and it was like 30 pages long!

When I get mine back, I will post it in GMA Resources for everyone...
« Last Edit: January 02, 2017, 06:11:17 pm by pi »
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iNerd

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Re: Insanely hard Q.
« Reply #13 on: November 14, 2010, 04:27:03 pm »
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Quote from: pi on November 14, 2010, 04:25:43 pm
Quote from: MBBS on November 14, 2010, 04:20:33 pm
Jesus Christ!

200 GMA kids, we have like 30!

The actual subject has been pretty easy thus far though.

our subject co-ordinator is some Indian guy with a phD in pure maths (yep, wtf!), and he made us do a third of the yr 12 course as well as the GMA course. Just for fun, he put random unit 1 methods stuff in as well and it was like 30 pages long!

When I get mine back, I will post it in GMA Resources for everyone...
He is not Indian. He is Lankan. Please respect his nationality.

Moderator action: removed real name, sorry for the inconvenience
« Last Edit: January 02, 2017, 06:11:29 pm by pi »
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lazykid

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Re: Insanely hard Q.
« Reply #14 on: November 16, 2010, 09:45:23 am »
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Quote from: MBBS on November 14, 2010, 04:20:33 pm
Jesus Christ!

200 GMA kids, we have like 30!


]

Jesus Christ! 30 GMA kids, we have like 11!
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