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Derive this identity from the sum and difference formulas for cosine:
sinasinb=1/2[cos(a-b)cos(a+b)]
Start with the right-hand side since it is more complex.
Calculations:
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_____
Reason:
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_____

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Don'tknowtrig

  1. look at the end of your last post of this same thing
    https://www.jiskha.com/display.cgi?id=1527528235

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    Reiny

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