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    How can I show
    6sin^2\theta=a+bcos2\theta

    What I did
    6(1-cos^2\theta)
    6-6cos^2\theta

    Stuck
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    (Original post by joyoustele)
    How can I show
    6sin^2\theta=a+bcos2\theta
    6(1-cos^2\theta)
    6-6cos^2\theta

    Stuck
    Use \frac{1}{2}(\cos 2 \theta +1)= \cos^2 \theta
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    (Original post by joyoustele)
    How can I show
    6sin^2\theta=a+bcos2\theta

    What I did
    6(1-cos^2\theta)
    6-6cos^2\theta

    Stuck
    Have you tried using cos 2A = 2cos^2 A - 1 so cos^A = ...
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    (Original post by RDKGames)
    Use \frac{1}{2}(\cos 2 \theta +1)= \cos^2 \theta
    Oh ... Thanks a lot
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    (Original post by RDKGames)
    Use \frac{1}{2}(\cos 2 \theta +1)= \cos^2 \theta
    You need to explain where that comes from as it's not a given identity.
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    (Original post by Muttley79)
    You need to explain where that comes from as it's not a given identity.
    I know. where it's from its just 1/2 of cos2x, then rearranged for cos^2x
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    (Original post by Muttley79)
    You need to explain where that comes from as it's not a given identity.
    Identity for \cos 2\theta obviously. OP is good enough to figure that one on their own.
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    (Original post by RDKGames)
    Identity for \cos 2\theta obviously. OP is good enough to figure that one on their own.
    Yes but if you just do as you suggest marks would be lost -
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    (Original post by Muttley79)
    Yes but if you just do as you suggest marks would be lost -
    Maybe, maybe not. The fact remains that I'm not telling them what to write word for word in an exam. That's up to them to formulate. I only stated what they need to use.
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    (Original post by joyoustele)
    I know. where it's from its just 1/2 of cos2x, then rearranged for cos^2x
    Yes but you woud need to show this or you will lose marks
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    (Original post by RDKGames)
    Maybe, maybe not. The fact remains that I'm not telling them what to write word for word in an exam. That's up to them to formulate. I only stated what they need to use.
    That's not helpful imho - C3 marking is extremly strict on these questions. If you don't give a reason you lose marks - fact.
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    (Original post by Muttley79)
    Yes but you woud need to show this or you will lose marks
    Dw, I always show my workings

    TY for the help. I highly appreciate it
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    (Original post by joyoustele)
    Dw, I always show my workings

    TY for the help. I highly appreciate it
    The mark scheme is usually particularly harsh for this topic - explain in words what you are doing.
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    (Original post by Muttley79)
    The mark scheme is usually particularly harsh for this topic - explain in words what you are doing.
    On here?
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    (Original post by joyoustele)
    On here?
    No, in the exam- but any hints on here should model good practice; hence my comment to RDKGames.
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    Oh shoot, I thought that this was about C3 photosynthesis.
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    (Original post by Muttley79)
    No, in the exam- but any hints on here should model good practice; hence my comment to RDKGames.
    Okay, Thanks...Im trying to go for an A* I dont want to lose any marks, Thanks a lot.
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    (Original post by joyoustele)
    Okay, Thanks...Im trying to go for an A* I dont want to lose any marks, Thanks a lot.
    Well you definitely don't need to explain anything 'in words' to get an A* so don't worry about this too much.
 
 
 
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