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# Current Year 13 thread Mark I (2014-2015) watch

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1. (Original post by rachelc142)
Would anybody mind helping with a c3 trig question

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Sure thing.
2. (Original post by The Financier)
Sure thing.
Thankyou

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

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3. (Original post by rachelc142)
Thankyou

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

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Latex pls T_T

I'll give it a go now
4. (Original post by Bude8)
Latex pls T_T

I'll give it a go now
Ty
Sorry for having to type it out messily can't figure out uploading pics on here on my phone

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5. (Original post by rachelc142)
Ty
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.
6. (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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7. (Original post by rachelc142)
Ty
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:

Multiplying by and using Pythagorean identity:

Set it equal to 0, and it'll factorise. I think that's how it's done.
8. (Original post by rachelc142)
Thankyou

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

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I believe Bude has done it right
9. (Original post by Bude8)
Rewriting the equation:

Multiplying by and using Pythagorean identity:

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

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10. (Original post by rachelc142)
Thanks so much!

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Couldn't you find the mark scheme though?
11. (Original post by Bude8)
Couldn't you find the mark scheme though?
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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12. (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
13. (Original post by Bude8)
You could try googling the problem
Yeah true
With stuff like this I'll always go to classmates first, then the student room, then examsolutions hahah

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14. (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/
15. Oooh will have to check that out

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

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17. (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?
18. (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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19. (Original post by rachelc142)
Sorry if it seems so simple to you

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20. (Original post by L'Evil Fish)
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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