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FP3 hyperbolic differentiation help Watch

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    How do you differentiate -tanh(x)sech(x)? Whenever I do it (using the product rule) I get sech(x)tanh^2(x) - sech^3(x), but the answer in the Solution Bank is sech^3(x) - sech(x)tanh^2(x). I don't know if I'm making a stupid error somewhere, or if I'm using the wrong rule.

    Will rep any answers that clear this up. Cheers
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    (Original post by ChrisP97)
    How do you differentiate -tanh(x)sech(x)? Whenever I do it (using the product rule) I get sech(x)tanh^2(x) - sech^3(x), but the answer in the Solution Bank is sech^3(x) - sech(x)tanh^2(x). I don't know if I'm making a stupid error somewhere, or if I'm using the wrong rule.

    Will rep any answers that clear this up. Cheers
    Your working is completely correct. Ignore the solution bank. I have just worked it out myself and I'm getting the same answer as yours.
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    (Original post by ChrisP97)
    How do you differentiate -tanh(x)sech(x)? Whenever I do it (using the product rule) I get sech(x)tanh^2(x) - sech^3(x), but the answer in the Solution Bank is sech^3(x) - sech(x)tanh^2(x). I don't know if I'm making a stupid error somewhere, or if I'm using the wrong rule.

    Will rep any answers that clear this up. Cheers
    Differential of sech(x) = -sech(x)tanh(x) can prove this by the quotient rule (remember unlike in trig, diff of cosh = sinh, not -sinh. Differential of -tanh(x) = -sech^2 (x), then just apply the product rule and bingo
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    (Original post by MathsAstronomy12)
    Differential of sech(x) = -sech(x)tanh(x) can prove this by the quotient rule (remember unlike in trig, diff of cosh = sinh, not -sinh. Differential of -tanh(x) = -sech^2 (x), then just apply the product rule and bingo
    I believe it's derivative and not differential?
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    (Original post by aymanzayedmannan)
    I believe it's derivative and not differential?
    Yeh my bad haha
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    (Original post by aymanzayedmannan)
    Your working is completely correct. Ignore the solution bank. I have just worked it out myself and I'm getting the same answer as yours.
    (Original post by MathsAstronomy12)
    Differential of sech(x) = -sech(x)tanh(x) can prove this by the quotient rule (remember unlike in trig, diff of cosh = sinh, not -sinh. Differential of -tanh(x) = -sech^2 (x), then just apply the product rule and bingo
    Ok great thanks, at least I'm doing it correct. I wish Edexcel would bother checking the resources they publish instead of leaving it to students to find the mistakes :/
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    (Original post by ChrisP97)
    leaving it to students to find the mistakes :/
    you learn better that way ,,,
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    (Original post by ChrisP97)
    Ok great thanks, at least I'm doing it correct. I wish Edexcel would bother checking the resources they publish instead of leaving it to students to find the mistakes :/
    The FP2 book has some pretty bad ones. I won't even get into the M2 book.
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    (Original post by ChrisP97)
    Ok great thanks, at least I'm doing it correct. I wish Edexcel would bother checking the resources they publish instead of leaving it to students to find the mistakes :/
    I don't think the Solution Bank is made by Edexcel (that is if we are talking about the same one).
 
 
 
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