# Maths (Harmonic equations)

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#1
How does one find the value of the constant k for.... sin θ+Root(2)Cos θ=k
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3 years ago
#2
What.
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#3
How do i find k, in this question?

sinθ+√2cosθ=k

Answer is -√3≤k≤√3, but how do i arrive at that?
Its core 3 AlevelMaths under the trigonometry topic.
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3 years ago
#4
(Original post by joyoustele)
How do i find k, in this question?

sinθ+√2cosθ=k

Answer is -√3≤k≤√3, but how do i arrive at that?
Its core 3 AlevelMaths under the trigonometry topic.
Let f(x) = sinθ+√2cosθ

Put it in the form of Rcos(θ + a)

Work out the range of that function and that'll give you k
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#5
(Original post by AnIndianGuy)
Let f(x) = sinθ+√2cosθ

Put it in the form of Rcos(θ + a)

Work out the range of that function and that'll give you k
Thank you so much, Now that you said it, it seems so obvious. How did you come to realise i needed to find the range?
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#6
(Original post by AnIndianGuy)
You can't really solve for theta because you don't know what k is, so you just try simplify it and see where that takes you.

Also I've done that question before
The very same? was it from a book or from TSR?
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#7
What Grade did you get in Alevel Maths? im aiming for an A at the moment.
(Original post by AnIndianGuy)
I think it was a C3 paper
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3 years ago
#8
(Original post by joyoustele)
How does one find the value of the constant k for.... sin θ+Root(2)Cos θ=k
you can find R and α to get RCos(θ - α)

but they would have to tell you a value for k.
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#9
(Original post by AnIndianGuy)
I'm Year 13, I was supposed to get an A* but my brain melted in the C3 exam due to how hot it was and me leaving my water bottle in the fridge. I expect an A but I may get an A*. I'll probably average 90% in total though, which sucks
Jeez, Do you have any tips for year 13? i have just finished year 12 and we will start year 13 in september but and i have already learnt nearly all of c3. will be moving on to c4.

What should i do to ACE year 13?
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#10
(Original post by the bear)
you can find R and α to get RCos(θ - α)

but they would have to tell you a value for k.
No there is no value for k, but someone already explained so i get it now, But thank you very much.
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#11
(Original post by AnIndianGuy)
Revise from the get go. A paper a week for Maths and don't hesitate to do IAL C34 papers.

Go over your weaknesses once you identify them. There's no point in doing papers unless you improve areas in which you consistently fail in.

Try and revise backwards too once you finish A2 so your AS content is fresh in your mind
So when i finish A2 revise AS as well(c1 and c2?)
-thank you, i will do a paper a week
- I do ocr not Edexcel, should i still do the IAL papers, since ocr and edexecel are similar or just do normal papers and ocr solomon papers?
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