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    Question 13

    This what I've done so far: = sin(a+b)/cos(a-b)

    = sinAcosB + cosAsinA / cosAcosB - sinAsinB
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    Try using the right hand side, making it into 1/(tan1/2(B-A)) and using the formula for tan(B-A) that you're given and expanding. Then see how you can work them to be the same.
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    Still can't do it
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    Oh, you made a mistake right off the bat. SinA + SinB is not the same as Sin(A+B), and same for the CosA - CosB.

    This is a mistake made very often, try make sure not to do it
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    Use the sum to product formulae.
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    (Original post by electriic_ink)
    Use the sum to product formulae.
    Never heard of that before
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    (Original post by The Shanus)
    Oh, you made a mistake right off the bat. SinA + SinB is not the same as Sin(A+B), and same for the CosA - CosB.

    This is a mistake made very often, try make sure not to do it
    So what can I do?
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    (Original post by Vorsah)
    So what can I do?
    There are loads of things you can do, but some will take ages. I would probably do it in a way that would take ages, and that would be what I said earlier. Leave the LHS (Left-Hand Side) how it is, and just get the RHS into Sin's and Cos's.
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    (Original post by Vorsah)
    Never heard of that before
    I'm pretty sure you will have formulae in your formula book that tell you how to rewrite things like sinA + sinB in the form of something like ksinPcosQ and similarly for the cos part of the formula.

    These should make the problem a lot simpler for you!
 
 
 
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