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verifying trig equations + exponential issues. watch

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    So i'm working on some problems for a math packet and I'm a bit stuck...


    sin2x - cos2x = tanx ....prove


    then there's this one, which i have no idea how to start really...
    2^x + 3(2^{x-1}) = 80

    help please...


    edit - i misread my notes, thanks guy below me, but still i haven't gotten much further...
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    cos2x doesn't expand to cos^2x + sin^2x
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    (Original post by Anick14)
    sin2x - cos2x = tanx ....prove
    it would be hard to prove this, it isn't true
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    (Original post by john1234567)
    it would be hard to prove this, it isn't true

    ha that definitely helps. my friends and i have been trying to figure this out and refused to believe that "it just isn't true" is a proper response. thanks for the verification.
 
 
 
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Updated: January 25, 2010

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