Basic Trigonometry
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Basic Trigonometry
Find the radius 'r'(?) of the circle 'C' in the attachment.
I know AO = OB = 6cm
Where the circle touches the circumference is pi/2 (90deg).
AOC = pi/6 = (30deg).
I have no idea what to do to find r. I am unable to use the sin/cosine rules as I don't have enough information..
Can anyone give me any pointers?Last edited by Joshmeid; 10-04-2012 at 19:19. -
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Re: Basic TrigonometryIs this not one of the most talked about C2 questions in recent years?(Original post by Joshmeid)
Find the radius 'r'(?) of the circle 'C' in the attachment.
I know AO = OB = 6cm
Where the circle touches the circumference is pi/2 (90deg).
AOC = pi/6 = (30deg).
I have no idea what to do to find r. I am unable to use the sin/cosine rules as I don't have enough information..
Can anyone give me any pointers?
Anyway extend OC to the arc AB. Can you now determine
if I say that 
. Simple trig from there
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Re: Basic TrigonometrySee the diagram below:(Original post by Joshmeid)
Find the radius 'r'(?) of the circle 'C' in the attachment.
I know AO = OB = 6cm
Where the circle touches the circumference is pi/2 (90deg).
AOC = pi/6 = (30deg).
I have no idea what to do to find r. I am unable to use the sin/cosine rules as I don't have enough information..
Can anyone give me any pointers?
Use sin in the blue triangle and you are done.
Spoiler:Show
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Re: Basic Trigonometry(Original post by TheMagicMan)
Anyway extend OC to the arc AB. Can you now determine if I say that . Simple trig from there
a = 6-|OC|
a = radius
OC/Sin(pi/2) = a/Sin(pi/6)
OC/Sin(pi/2) = 6 - |OC|/Sin(pi/6)
Sin(pi/6)|OC|/Sin(pi/2) = 6 - |OC|
1/2|OC| = 6 - |OC|
|OC| = 12 - 2|OC|
3|OC| = 12
|OC| = 4
___________
a = 6 - |OC|
a = 6 - 4
a = 2
Therefore Radius = 2. Is this correct?Last edited by Joshmeid; 11-04-2012 at 19:35. -
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Re: Basic TrigonometryI believe so.(Original post by Joshmeid)
|OC| + a = 6
a = 6 - |OC|
a = radius
OC/Sin(pi/2) = a/Sin(pi/6)
OC/Sin(pi/2) = 6 - |OC|/Sin(pi/6)
Sin(pi/6)|OC|/Sin(pi/2) = 6 - |OC|
1/2|OC| = 6 - |OC|
|OC| = 12 - 2|OC|
3|OC| = 12
|OC| = 4
___________
a = 6 - |OC|
a = 6 - 4
a = 2
Therefore Radius = 2. Is this correct? -
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Re: Basic TrigonometryYes, it is.(Original post by TheMagicMan)
Is this not one of the most talked about C2 questions in recent years?
It came in the june 2011 edexcel C2 paper, and this question cost me 100 that day
. Though its a simple question but that day the exam conditions also played its part, and i failed to find the radius.
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Re: Basic TrigonometryYes, it is correct, but the working is too long, see the method i have done in the spoiler.(Original post by Joshmeid)
|OC| + a = 6
a = 6 - |OC|
a = radius
OC/Sin(pi/2) = a/Sin(pi/6)
OC/Sin(pi/2) = 6 - |OC|/Sin(pi/6)
Sin(pi/6)|OC|/Sin(pi/2) = 6 - |OC|
1/2|OC| = 6 - |OC|
|OC| = 12 - 2|OC|
3|OC| = 12
|OC| = 4
___________
a = 6 - |OC|
a = 6 - 4
a = 2
Therefore Radius = 2. Is this correct? -
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Re: Basic TrigonometryI sat this paper, and used a reasonably complicated argument involving incircles and inversion...the examiner was undoubtedly not happy...when I saw the approved solution later I was(Original post by raheem94)
Yes, it is.
It came in the june 2011 edexcel C2 paper, and this question cost me 100 that day. Though its a simple question but that day the exam conditions also played its part, and i failed to find the radius.
Last edited by TheMagicMan; 10-04-2012 at 19:12. -
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Re: Basic TrigonometryThe ones who sat this paper won't forget this question, like me.(Original post by TheMagicMan)
I sat this paper, and used a reasonably complicated argument involving incircles and inversion...the examiner was undoubtedly not happy...when I saw the approved solution later I was
You would have probably got 100 in it, right?
Which other modules do you do? -
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Re: Basic TrigonometryI did not get 100, as I was marked down on this question, despite the fact I used a perfectly valid method...it was too late for a remark(Original post by raheem94)
The ones who sat this paper won't forget this question, like me.
You would have probably got 100 in it, right?
Which other modules do you do?
I do C1-4. FP1-3, S1-3, M1-3 examined, and I've studied M4-5 for interest's sakes -
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Re: Basic TrigonometryI hate the exam conditions.. Always costing easy marks..(Original post by raheem94)
It came in the june 2011 edexcel C2 paper, and this question cost me 100 that day. Though its a simple question but that day the exam conditions also played its part, and i failed to find the radius.
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Re: Basic TrigonometryI have done C1-4, FP1 and M1-3. Will be taking FP2-3, S1-2 in june along with AEA.(Original post by TheMagicMan)
I did not get 100, as I was marked down on this question, despite the fact I used a perfectly valid method...it was too late for a remark
I do C1-4. FP1-3, S1-3, M1-3 examined, and I've studied M4-5 for interest's sakes
How do you find S1?
I am doing it nowadays, and hating it. Its completely illogical, right?
Did you took M3 in jan 2012? -
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Re: Basic TrigonometryActually that day i was more prepared for chemistry rather than maths, so i couldn't solve challenging questions.(Original post by Joshmeid)
I hate the exam conditions.. Always costing easy marks..
Exam conditions don't always cost me marks, though they can cost me around 3 marks at times. -
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Re: Basic TrigonometryI hated S1 as well-I think everyone does. I'm taking M3 in June.(Original post by raheem94)
I have done C1-4, FP1 and M1-3. Will be taking FP2-3, S1-2 in june along with AEA.
How do you find S1?
I am doing it nowadays, and hating it. Its completely illogical, right?
Did you took M3 in jan 2012? -
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Re: Basic TrigonometryBy the way, do you find a lot of difference in S1 methods between different boards?(Original post by TheMagicMan)
I hated S1 as well-I think everyone does. I'm taking M3 in June.
I think all boards do it differently.
How is S2?
How much time does it takes to prepare, is it more logical?
How is FP3?
I am yet to prepare FP3, S2 while S1 is only half done.
Do you do physics with edexcel? -
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Re: Basic Trigonometryyh this was the paper that i sat in june(Original post by TheMagicMan)
Is this not one of the most talked about C2 questions in recent years?
Anyway extend OC to the arc AB. Can you now determine if I say that . Simple trig from there
got 74 for it, was my worst one
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Re: Basic TrigonometryNo idea(Original post by raheem94)
By the way, do you find a lot of difference in S1 methods between different boards?
Not much better(Original post by raheem94)
How is S2?
(Original post by raheem94)
How much time does it takes to prepare, is it more logical?
It's just as easy as S1, but there's no justification for why you do anything.
It's the most interesting of any of the maths modules(Original post by raheem94)
How is FP3?
(Original post by raheem94)
Do you do physics with edexcel?
No WJEC. -
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Re: Basic TrigonometryThanks(Original post by TheMagicMan)
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Re: Basic TrigonometryAnyone doing MEI here? Heard you can get 3.5 maths A-Levels. Is that true?(Original post by raheem94)
Thanks
. Though its a simple question but that day the exam conditions also played its part, and i failed to find the radius.
