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Current Year 13 thread Mark I (2014-2015)

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Thankyou :smile:

So its
'Solve 2cot(^2)3theta=7cosec 3theta -5 for 0-theta-180deg'

Basically I tried using identities with the assumption cot^2theta +1 = cosec^2theta works for all multiples of theta

So I let cot(^2)3theta =cosec (^2)3theta -1
Multiplied the bracket out and rearranged to get
5cosec(^2)3theta = 3
Square rooted and rerranged for
Sin3theta = 5 / root15

And was going to solve like a c2 trig question but obviously cant do that as 5/root15 > 1
Do I need to implement multiple angle formulas? Or did I go wrong somewhere further up?
Thanks so much :smile:

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Original post by rachelc142
Thankyou :smile:

So its
'Solve 2cot(^2)3theta=7cosec 3theta -5 for 0-theta-180deg'

Basically I tried using identities with the assumption cot^2theta +1 = cosec^2theta works for all multiples of theta

So I let cot(^2)3theta =cosec (^2)3theta -1
Multiplied the bracket out and rearranged to get
5cosec(^2)3theta = 3
Square rooted and rerranged for
Sin3theta = 5 / root15

And was going to solve like a c2 trig question but obviously cant do that as 5/root15 > 1
Do I need to implement multiple angle formulas? Or did I go wrong somewhere further up?
Thanks so much :smile:

Posted from TSR Mobile


Latex pls T_T

I'll give it a go now
Original post by Bude8
Latex pls T_T

I'll give it a go now


Ty :smile:
Sorry for having to type it out messily can't figure out uploading pics on here on my phone

Posted from TSR Mobile
Original post by rachelc142
Ty :smile:
Sorry for having to type it out messily can't figure out uploading pics on here on my phone

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Can you use a calculator for C3?

edit: think I've done it, I'll start typing it up.
(edited 9 years ago)
Original post by Bude8
Can you use a calculator for C3?


Yeah, I'm with edexcel so not sure if its different for other exam boards but this is taken from a calc paper

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Original post by rachelc142
Ty :smile:
Sorry for having to type it out messily can't figure out uploading pics on here on my phone

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Rewriting the equation:

2tan⁡23θ=7sin⁡3θ−5\dfrac{2}{\tan^2 3\theta}=\dfrac{7}{\sin 3\theta}-5

2cos⁡23θsin⁡23θ=7sin⁡3θ−5\dfrac{2 \cos^2 3 \theta}{\sin^2 3\theta}=\dfrac{7}{\sin 3\theta}-5

Multiplying by sin⁡23θ\sin ^2 3\theta and using Pythagorean identity:

2−2sin⁡23θ=7sin⁡3θ−5sin⁡23θ2-2 \sin^2 3\theta=7 \sin 3\theta - 5\sin^2 3 \theta

Set it equal to 0, and it'll factorise. I think that's how it's done.
Original post by Bude8
Rewriting the equation:

2tan⁡23θ=7sin⁡3θ−5\dfrac{2}{\tan^2 3\theta}=\dfrac{7}{\sin 3\theta}-5

2cos⁡23θsin⁡23θ=7sin⁡3θ−5\dfrac{2 \cos^2 3 \theta}{\sin^2 3\theta}=\dfrac{7}{\sin 3\theta}-5

Multiplying by sin⁡23θ\sin ^2 3\theta and using Pythagorean identity:

2−2sin⁡23θ=7sin⁡3θ−5sin⁡23θ2-2 \sin^2 3\theta=7 \sin 3\theta - 5\sin^2 3 \theta

Set it equal to 0, and it'll factorise. I think that's how it's done.


Thanks so much!

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Original post by rachelc142
Thanks so much!

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Couldn't you find the mark scheme though? :lol:
Original post by Bude8
Couldn't you find the mark scheme though? :lol:


The teacher gave us a booklet of c3 past paper questions but didnt put which papers each question is from
And I seriously don't want to go through every single c3 paper to find it haha

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Original post by rachelc142
The teacher gave us a booklet of c3 past paper questions but didnt put which papers each question is from
And I seriously don't want to go through every single c3 paper to find it haha

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You could try googling the problem :tongue:
Original post by Bude8
You could try googling the problem :tongue:


Yeah true
With stuff like this I'll always go to classmates first, then the student room, then examsolutions hahah

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Original post by rachelc142
Yeah true
With stuff like this I'll always go to classmates first, then the student room, then examsolutions hahah

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my go to --> http://math.stackexchange.com/ :lol:
Original post by Bude8


Oooh will have to check that out

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Has anybody done Taylor expansion yet in fp2 (edexcel)?
Having to self teach it and finding it really tricky

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Original post by rachelc142
Has anybody done Taylor expansion yet in fp2 (edexcel)?
Having to self teach it and finding it really tricky

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Is it literally not just differentiating a function and subbing a value of x-a in?
Original post by L'Evil Fish
Is it literally not just differentiating a function and subbing a value of x-a in?


Sorry if it seems so simple to you

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Original post by rachelc142
Sorry if it seems so simple to you

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No I'm asking :lol:
Original post by L'Evil Fish
No I'm asking :lol:


I might be overcomplicating it but I really don't understand it
I have a very vague teacher and feel that I haven't understood anything so far this year
Also haven't done differentiating trig in c3 yet so that complicates matters

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Original post by rachelc142
I might be overcomplicating it but I really don't understand it
I have a very vague teacher and feel that I haven't understood anything so far this year
Also haven't done differentiating trig in c3 yet so that complicates matters

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You might struggle then, because you'll need C3 differentiation

Do you have an example of the type of question they'd ask?
Will be an Official Adult™ tomorrow :woo:

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