Hi everyone,

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

(Itwasntme)

Printable View

- Sep 13th 2008, 04:03 AMvalerie-petitMathcad 2001
Hi everyone,

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

(Itwasntme) - Sep 13th 2008, 04:27 AMPlato
Post exactly what you are trying to do.

Post a screen-shot if possible. - Sep 13th 2008, 05:40 AMvalerie-petitDifferentiation
[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(Headbang)

[IMG]file:///C:/DOCUME%7E1/OPENUN%7E1/LOCALS%7E1/Temp/moz-screenshot-7.jpg[/IMG] - Sep 13th 2008, 05:52 AMPlato
This is what MathCad gives me.

- Sep 13th 2008, 06:27 AMvalerie-petitre: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 - Sep 13th 2008, 06:31 AMTKHunny
- Sep 13th 2008, 06:40 AMPlato
Here is the next question.

- Sep 13th 2008, 07:13 AMvalerie-petitre: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 - Sep 13th 2008, 07:23 AMPlato
Two points.

Why do you have $\displaystyle x:=x$?

Try using $\displaystyle (8 \cdot x)$ instead of $\displaystyle 8x$. - Sep 13th 2008, 07:32 AMvalerie-petitre:mathcad
It works for simplify(Clapping)(Clapping)(Clapping), you were right I put 8x under brackets and it works(Giggle)(Rofl)

- Sep 13th 2008, 07:35 AMvalerie-petitre: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.

- Sep 13th 2008, 07:52 AMPlato
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.

- Sep 13th 2008, 08:03 AMvalerie-petitre: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(Worried) - Sep 13th 2008, 08:20 AMPlato
- Sep 13th 2008, 08:28 AMvalerie-petitre: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?