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# Edexcel A2 C3 Mathematics 12th June 2015 watch

1. https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf

why is 2x= 90, 270?

for question 8 for 1 solution

tanx graph cuts at 180,0 and 360?
2. (Original post by Freddy-Francis)
But wastes time looking back :P

Do u really need to check
Nah im just saying cos if people forgot the rule in the exam due to pressure then they know they can look in the formula booklet
3. (Original post by Sants)
Nah im just saying cos if people forgot the rule in the exam due to pressure then they know they can look in the formula booklet
oh ok
4. (Original post by studentwiz)
what do you have to say for the sign change iteration proof question to get full marks
There is a sign change and f (x) is continuous therefore there is a root in the interval [a, b]

But usually sign change alone should suffice
5. I just did the hardest gold paper. It was way easier than the June 2014 R paper
6. (Original post by Freddy-Francis)
I just did the hardest gold paper. It was way easier than the June 2014 R paper
I know right! That's because the June 2014 R paper was all round disgusting, whereas the gold papers are combined 'harder' questions from all years.
7. (Original post by studentwiz)
https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf

why is 2x= 90, 270?

for question 8 for 1 solution

tanx graph cuts at 180,0 and 360?
i didnt get that

I got x = 45 , 135
and x = 22.5, 112.5
8. Which one are the edexcel more likely to ask us to do?
Rcos(x+a)
Rcos(x-a)
Rsin(x+a)
Rsin(x-a)
9. (Original post by Sants)
Which one are the edexcel more likely to ask us to do?
Rcos(x+a)
Rcos(x-a)
Rsin(x+a)
Rsin(x-a)
doesnt matter does it ?
10. (Original post by Sants)
Which one are the edexcel more likely to ask us to do?
Rcos(x+a)
Rcos(x-a)
Rsin(x+a)
Rsin(x-a)
They usually ask the + ones
11. (Original post by Sants)
Which one are the edexcel more likely to ask us to do?
Rcos(x+a)
Rcos(x-a)
Rsin(x+a)
Rsin(x-a)
Any of them.
Also quickly learn which one is use ful inndifferent cases as if edexcel wanted to be really bad they could just ask you to put it into harmonic form without saying which type.

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12. (Original post by studentwiz)
https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf

why is 2x= 90, 270?

for question 8 for 1 solution

tanx graph cuts at 180,0 and 360?
When cot2x = 0

cos2x/sin2x = 0 (multiply by sin2x)

gives us cos2x = 0

Then you solve for the 2 solutions from there.
13. (Original post by Freddy-Francis)
i didnt get that

I got x = 45 , 135
and x = 22.5, 112.5
was that for cot2x=1 or cot2x=0 ?
14. (Original post by AenigmaFx)
When cot2x = 0

cos2x/sin2x = 0 (multiply by sin2x)

gives us cos2x = 0

Then you solve for the 2 solutions from there.
oh forgot about that that thanks so much
15. What do I do if with the Rcos(..) the tan comes out as minus?

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16. (Original post by studentwiz)
was that for cot2x=1 or cot2x=0 ?
yes

Cot(2x) = 0
1/Tan(2x) = 0
Cos(2x)/Sin(2x) = 0
so Cos(2x) = 0
2x =90 and i used cast diagram to get the other solution

Cot(2x) =1
1/tan(2x) =1
1= tan(2x)
so 2x =45
17. (Original post by sorarosa1998)
What do I do if with the Rcos(..) the tan comes out as minus?

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then u did something wrong

I hope edexcel wont do that
18. (Original post by physicsmaths)
Any of them.
Also quickly learn which one is use ful inndifferent cases as if edexcel wanted to be really bad they could just ask you to put it into harmonic form without saying which type.

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wat do u mean
19. (Original post by Freddy-Francis)
yes

Cot(2x) = 0
1/Tan(2x) = 0
Cos(2x)/Sin(2x) = 0
so Cos(2x) = 0
2x =90 and i used cast diagram to get the other solution

Cot(2x) =1
1/tan(2x) =1
1= tan(2x)
so 2x =45
thank you, there was 4 answers for that question btw
20. Like when I compare coefficients one answer is minus? Then it will be tan -x/y
Usually it's plus never came across a minus but askin jic

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