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Math Help - Mathcad 2001

  1. #1
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    Post Mathcad 2001

    Hi everyone,

    Is anyone familiar with Mathcad 2001, I have an exercise on differientiation cannot make work

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  2. #2
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    Post exactly what you are trying to do.
    Post a screen-shot if possible.
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  3. #3
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    Smile Differentiation

    [IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot.jpg[/IMG][IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-1.jpg[/IMG][IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-2.jpg[/IMG][IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-3.jpg[/IMG][IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-4.jpg[/IMG] I have to use the symbolic differentiation and the 'simplify' keyword to find an expression for the derivative of f'(x). (you may need to put x=x in your worksheet)
    Now my function is

    f(x)= 8x(5-2x)(13+2x)/(2+x)^2

    When I simplify it give



    8x(5-2x) (13+2x)/(2+x)^2


    It doesn't look right for a derivative of f'(x), it just change to (13+2x)/(2+x)^2.



    Hope you understand. I try screenshot and attached my file, it's not working



    [IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-7.jpg[/IMG]
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  4. #4
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    This is what MathCad gives me.
    Attached Thumbnails Attached Thumbnails Mathcad 2001-mathcad.gif  
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  5. #5
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    Smile re:mathcad

    Oh, I try the dx function but it is not working for me. Next exercise ask to solve the equation f'(x)=0 (using a solve block), I try with your result and give me a massive page of calculation, but they ask the answer to 6 d.p.

    Don't know what I'm doing wrong
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  6. #6
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    Quote Originally Posted by valerie-petit View Post
    f'(x), it just change to (13+2x)/(2+x)^2
    That certainly makes no sense. My first suspicion is an input error.

    How careful are you to use EXPLICIT multiplication when you enter your expressions?

    Are you SURE you don't have part of your expression entered as text?
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  7. #7
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    Here is the next question.
    Attached Thumbnails Attached Thumbnails Mathcad 2001-mathcad2.gif  
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  8. #8
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    Smile re:mathcad

    [IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-11.jpg[/IMG][IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-12.jpg[/IMG]

    I attached my files, the first line I try under f(x), the Third line is the way you did it with dx and the middle one is when I try to solve it.

    Hope the attachment works
    Attached Thumbnails Attached Thumbnails Mathcad 2001-math2.jpg  
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  9. #9
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    Two points.
    Why do you have x:=x?
    Try using (8 \cdot  x) instead of 8x.
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  10. #10
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    re:mathcad

    It works for simplify, you were right I put 8x under brackets and it works
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  11. #11
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    re:mathcad

    Sorry Plato with all my questions, but in the second question to solve the equation f'(x)=0, it said that my answer should be in 6 decimal places, but like you it gave me different calculations not one result.
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  12. #12
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    Once you ask it to "solve for" and the blue backwards L is on the solution then type = key to change to decimal format. Once in decimal form, double click on a real number and you then can format the number of places you need.
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  13. #13
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    re:mathcad

    Ok, sorry I saw the calcution but didn't scroll to the end of my screen, I change in format to 6 d.p and it gave 0.8531; -3.42655+5.133725i etc...

    Did you find the same results
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  14. #14
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    Quote Originally Posted by valerie-petit View Post
    Ok, sorry I saw the calcution but didn't scroll to the end of my screen, I change in format to 6 d.p and it gave 0.8531; -3.42655+5.133725i etc...

    Did you find the same results
    Set not only the number of decimals but also the “exponential threshold”.
    The other two numbers are complex numbers. I think you want the real solutions.
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  15. #15
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    Unhappy re:mathcad

    Sorry Plato, I completely lost it.

    Do I need to go into format result, tolerance, threshold? do I need to change the complex threshold?
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