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# Edexcel A2 C3 Mathematics 12th June 2015 watch

1. (Original post by EspDe97)
Does anyone know how to do this question?

sin(A+B) - sin(A-B) / cos(A-B) - cos(A+B) = cotA
Using the result of part (b) and the exact values of sin 60° and cos 60°,
(c) find an exact value for cot 75°in its simplest form.
Can you show us the rest of the question?
2. Can anyone help me to understand how to find 2c?
As it's the inverse of f(x), the domain will be the range of f(x).. (right?) That's all I know

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3. (Original post by Sakchuu)
Hey, when finding/proving a root, do you sub the values into a) y=f(x) or b) f'(x)?
f(x)!!!
4. (Original post by studentwiz)
how would you use part a) to do b
this is how i would do it, havent checked the MS tho
5. (Original post by studentwiz)
how would you use part a) to do b
Please what paper is this from?
6. (Original post by studentwiz)
question 1 part b https://b3755649dbd1afe3db91a899c3b9...%20Edexcel.pdf

when Expand I get 9x^2-30x+24 but I dont get one solution being x=2 ?
Not sure where you went wrong, probably a simple factorizing error

7. (Original post by moeeahmed)
Can someone help me with this question please?

The function g is defined byg : x= ln(2x), x >0

(c) Solve the equation g(x) + g(x2) + g(x3) = 6 giving your answer in its simplest form.

The answer is (e/root2) June 2014(R) paper
Put x in for g(x) then x^2 in for g(x^2) then x^3 in for g(x^3). You'll get ln(2x) + ln(2x^2) + ln(2x^3) = 6
Use log laws to solve
8. (Original post by ridirahman)
Ohh okay I think I understand I will need to practice these type of questions more thanks for helping!
No problem man, good luck tomorrow!
9. (Original post by EspDe97)
Does anyone know how to do this question?

sin(A+B) - sin(A-B) / cos(A-B) - cos(A+B) = cotA
Using the result of part (b) and the exact values of sin 60° and cos 60°,
(c) find an exact value for cot 75°in its simplest form.
Since A=75

sin(75+15) -(sin75-15)/cos(75-15)-cos(75+15) =cot75 (value of B can be anything)
=> sin(90)-sin(60)/cos(60)-cos(90)=cot(75)
10. (Original post by anndz3007)
Since A=75

sin(75+15) -(sin75-15)/cos(75-15)-cos(75+15) =cot75 (value of B can be anything)
=> sin(90)-sin(60)/cos(60)-cos(90)=cot(75)
Thank you so much!
11. can anyone link me the June 2013 R paper? thanks!
12. So with maximums and stuff.
When R is maximum, cos(x+a)=-1 and R is minimum, cos(x+a)=1?

Am i right?
13. any tips or tricks to remember tomorrow?
14. (Original post by frozo123)
can anyone link me the June 2013 R paper? thanks!
All the papers you will ever need:
http://www.physicsandmathstutor.com/...rs/c3-edexcel/
15. what are the proofs for tomorrow do we need to remember?
16. Could someone please explain why g^-1gf(x)=f(x) ?

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17. (Original post by Nirm)
So with maximums and stuff.
When R is maximum, cos(x+a)=-1 and R is minimum, cos(x+a)=1?

Am i right?
Yes. However, there may be situations where the maximum value of a function including Rcos(x+a) is when cos(x+a) = -1 or even when it equals 0 - it depends on the context of the function
18. (Original post by TeddyKC)
Could someone please explain why g^-1gf(x)=f(x) ?

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g^-1(x) and g(x) are inverse functions and so they cancel each other out, in the same way that lne = 1
19. (Original post by Nirm)
So with maximums and stuff.
When R is maximum, cos(x+a)=-1 and R is minimum, cos(x+a)=1?

Am i right?
nahh depend on the situationn
20. (Original post by frozo123)
can anyone link me the June 2013 R paper? thanks!
http://www.physicsandmathstutor.com/...rs/c3-edexcel/

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