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C3 Mixed Exercise 7F Q9 Watch

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    Hi,

    I was wondering if anybody could help me, I am stuck on C3 Mixed Exercise 7F, Question 9 c and d.

    C - solve
    sin(θ+40°) + sin(θ+50°) = 0 , 0 ≤ θ ≤ 360°

    D - solve
    sin² θ/2 = 2sinθ ,0 ≤ θ ≤ 360°

    Any help would be appreciated as Physics and Math Tutors Solution jump around and don't really explain anything, which is annoying...

    Thanks!
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    (Original post by BenRichi_)
    Hi,

    I was wondering if anybody could help me, I am stuck on C3 Mixed Exercise 7F, Question 9 c and d.

    C - solve
    sin(θ+40°) + sin(θ+50°) = 0 , 0 ≤ θ ≤ 360°

    D - solve
    sin² θ/2 = 2sinθ ,0 ≤ θ ≤ 360°

    Any help would be appreciated as Physics and Math Tutors Solution jump around and don't really explain anything, which is annoying...

    Thanks!
    have you made any start?
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    sin(θ) = cos(90-θ)
    cos(θ) = sin(90 - θ)
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    (Original post by TeeEm)
    have you made any start?
    Well for C I started by using the addition formulae to expand, but was just left with nothing. And nothing for D
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    sin(x+50) = cos(x+40)
    So -tan(x+40) = 0
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    (Original post by NotNotBatman)
    sin(θ) = cos(90-θ)
    cos(θ) = sin(90 - θ)
    Where does this come from?
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    (Original post by BenRichi_)
    Well for C I started by using the addition formulae to expand, but was just left with nothing. And nothing for D
    does post 3 help?
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    (Original post by TeeEm)
    does post 3 help?
    Well I understand how I would use it, but don't understand where that is from, I have never seen this before?
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    (Original post by TeeEm)
    does post 3 help?
    Youre trying too much
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    (Original post by BenRichi_)
    Where does this come from?
    It's taught in c2. Draw a right angled triangle with an angle marked x, so the other angle will have to be 90-x and you'll see that it works.

    or consider the cosine and sine graphs.
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    (Original post by BenRichi_)
    Well I understand how I would use it, but don't understand where that is from, I have never seen this before?
    standard result taught at C2
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    (Original post by GeologyMaths)
    Youre trying too much
    I don't think that your solution works, or makes sense...
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    (Original post by BenRichi_)
    Well I understand how I would use it, but don't understand where that is from, I have never seen this before?
    cos(x) = sin(90-x)
    cos(x) = sin90cosx - sinxcos90
    cos(x) = cos(x) - 0
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    (Original post by BenRichi_)
    Hi,

    I was wondering if anybody could help me, I am stuck on C3 Mixed Exercise 7F, Question 9 c and d.

    C - solve
    sin(θ+40°) + sin(θ+50°) = 0 , 0 ≤ θ ≤ 360°

    D - solve
    sin² θ/2 = 2sinθ ,0 ≤ θ ≤ 360°

    Any help would be appreciated as Physics and Math Tutors Solution jump around and don't really explain anything, which is annoying...

    Thanks!
    Have u come across the factor formula? if not it is
    sinp+ sinq== 2sin(p+q/2)cos(p-q/2).... with p as 40° and q as 50°. Sub in values
    and you should come to 2sin(θ+45)=0 and cos(-5)=0 where cos(-5) is invalid therefore solve 2sin(θ+45)=0................... ...ok and tell me what you get
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    (Original post by raman_17)
    Have u come across the factor formula? if not it is
    sinp+ sinq== 2sin(p+q/2)cos(p-q/2).... with p as 40° and q as 50°. Sub in values
    and you should come to 2sin(θ+45)=0 and cos(-5)=0 where cos(-5) is invalid therefore solve 2sin(θ+45)=0................... ...ok and tell me what you get
    Thank you very much raman, I was just looking through the C3 book and found this, its the best solution and gives the correct answer!
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    (Original post by BenRichi_)
    Thank you very much raman, I was just looking through the C3 book and found this, its the best solution and gives the correct answer!
    no worries
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    (Original post by BenRichi_)
    Hi,

    I was wondering if anybody could help me, I am stuck on C3 Mixed Exercise 7F, Question 9 c and d.

    C - solve
    sin(θ+40°) + sin(θ+50°) = 0 , 0 ≤ θ ≤ 360°

    D - solve
    sin² θ/2 = 2sinθ ,0 ≤ θ ≤ 360°

    Any help would be appreciated as Physics and Math Tutors Solution jump around and don't really explain anything, which is annoying...

    Thanks!
    sin(x)=2sin(x/2)cos(x/2)
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    (Original post by BenRichi_)
    I don't think that your solution works, or makes sense...
    this person has been trolling the maths forum today.
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    (Original post by the bear)
    this person has been trolling the maths forum today.
    how?
 
 
 
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