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    i did a differentiation question and i wanted to know if its the right answer.

    the q is: [(x-1)/(2-x)]^2 and i got [2(x-1)]/[(2-x)^3] sorry dont know how to use latex.

    i havent done diff for ages so im a bit rusty and wanted to know if its right and if not, where im going wrong.

    thanks much appreciated

    btw i used the chain rule and differentiated it as a whole and for the bit inside the brackets i used the quotient rule.
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    I have got the same answer as you, I think you're right.
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    (Original post by Hormonal)
    I have got the same answer as you, I think you're right.
    thanks for having a look
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    i also have another question and i'd just like someone to check it for me.

    its: x=2cos(theta) and y=3sin(theta)

    find dy/dx in terms of theta, and the coordinates of the 2 turning points.

    my answer:
    Spoiler:
    Show
    I got dy/dx = 3cos(theta)/-2sin(theta)

    then at TP dy/dx = 0 so 3cos(theta) = 0.

    so theta must be 90 and/or 270.

    I subbed this back into the orig x and y and got the coordinates to be (0,3) and (0,-3).


    am I doing this right?

    thanks so much
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    (Original post by SurpriseMe)
    i also have another question and i'd just like someone to check it for me.

    its: x=2cos(theta) and y=3sin(theta)

    find dy/dx in terms of theta, and the coordinates of the 2 turning points.

    my answer:
    Spoiler:
    Show
    I got dy/dx = 3cos(theta)/-2sin(theta)

    then at TP dy/dx = 0 so 3cos(theta) = 0.

    so theta must be 90 and/or 270.

    I subbed this back into the orig x and y and got the coordinates to be (0,3) and (0,-3).


    am I doing this right?

    thanks so much
    This is correct, though if I were being picky I'd put the angles in radians
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    (Original post by joostan)
    This is correct, though if I were being picky I'd put the angles in radians
    lol, to be fair I did do it in radians cos my calc is always in that mode but then for some reason I just felt safer doing it in degrees cos i'm used to the angles at which the cos graph meets the x axis
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    (Original post by SurpriseMe)
    lol, to be fair I did do it in radians cos my calc is always in that mode but then for some reason I just felt safer doing it in degrees cos i'm used to the angles at which the cos graph meets the x axis
    Meh, it's only a technicality, I know lots of people who do the same thing
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    (Original post by joostan)
    Meh, it's only a technicality, I know lots of people who do the same thing
    yeah same here

    I have another question. How would you diff 2sin^3(e^x)?

    would you chnage it to 2[sin(e^x)]^3 and use the chain rule or something?
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    bump.

    How would you diff 2sin^3(e^x)?

    would you change it to 2[sin(e^x)]^3 and use the chain rule or something?

    thanks
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    bump
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    (Original post by SurpriseMe)
    bump.

    How would you diff 2sin^3(e^x)?

    would you change it to 2[sin(e^x)]^3 and use the chain rule or something?

    thanks
    Product Rule:

    y = (u)(v)

    dy/dx = (u')(v) + (u)(v')

    Okay. Ignore me actually. Wow
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    (Original post by SurpriseMe)
    bump.

    How would you diff 2sin^3(e^x)?

    would you change it to 2[sin(e^x)]^3 and use the chain rule or something?

    thanks
    Hey, yep it's just the chain rule with three steps:

    sin
    e^x
    [...]^3

    Multiply by the differential of all of those. Don't forget to include the 2 at the start as well!

    Hope that helps?



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    (Original post by L'Evil Fish)
    Product Rule:

    y = (u)(v)

    dy/dx = (u')(v) + (u)(v')
    Why product rule?


    (Original post by stuart_aitken)
    Hey, yep it's just the chain rule with three steps:

    sin
    e^x
    [...]^3

    Multiply by the differential of all of those. Don't forget to include the 2 at the start as well!

    Hope that helps?
    So it would be 6[sin(e^x)]^2 mutliplied by the differential of what's inside the brackets which is e^xcos(e^x)? Is my differential inside the bracket correct?
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    (Original post by L'Evil Fish)
    Product Rule:

    y = (u)(v)

    dy/dx = (u')(v) + (u)(v')

    Okay. Ignore me actually. Wow
    What lol? I'm so confused

    you're probably way better at maths than i so.... :/
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    (Original post by SurpriseMe)
    What lol? I'm so confused

    you're probably way better at maths than i so.... :/
    I thought we could use it like this:

    2Sin^3(e^x)

    But then I realised there wasn't an x after Sin^3.

    And yes, your differential outside the bracket is right
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    (Original post by L'Evil Fish)
    I thought we could use it like this:

    2Sin^3(e^x)

    But then I realised there wasn't an x after Sin^3.

    And yes, your differential outside the bracket is right
    Ohhh yeah that would make sense :yes:

    thank you for checking as well
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    (Original post by SurpriseMe)
    Ohhh yeah that would make sense :yes:

    thank you for checking as well
    No problem, my confidence has been knocked a little so I'm wary of answering but I do it anyway:lol:
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    (Original post by L'Evil Fish)
    No problem, my confidence has been knocked a little so I'm wary of answering but I do it anyway:lol:
    haha, well as you can see my confidence isn't exactly tip-top otherwise I wouldn't keep asking how to do questions that I'm getting right

    well I don't blame you cos if you gave a wrong answer you might have a billion quotes questioning your abilities lol. That's why I stay far away from even answering gcse question
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    (Original post by SurpriseMe)
    haha, well as you can see my confidence isn't exactly tip-top otherwise I wouldn't keep asking how to do questions that I'm getting right

    well I don't blame you cos if you gave a wrong answer you might have a billion quotes questioning your abilities lol. That's why I stay far away from even answering gcse question
    Fair enough :five:

    Yeah, lately I've been getting a bit wrong so I haven't answered in a while :ahee:

    What year are you in now?
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    (Original post by L'Evil Fish)
    Fair enough :five:

    Yeah, lately I've been getting a bit wrong so I haven't answered in a while :ahee:

    What year are you in now?
    :five:

    I'm in year 13, i'm supposed to be an A* student but i think i lack a bit of self-confidence sometimes and i hate being wrong lol :/
 
 
 
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